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Oceanography 101

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Chapter 1 - Introduction to Oceanography

Note to students: This website is an extended version of course notes for an introductory course in Oceanography at MiraCosta College, Fall, 2015. Selected links are provided as "required reading" of material that supplement information presented in class and during field trips. The summarized content and graphic images presented here are the same used in course lectures and will be used on quizzes and exams.

*** Science involves a language in addition to concepts! So be prepared! ***

What is oceanography?

Oceanography includes the branches of science that deal with the physical and biological properties, and observable phenomena of the world oceans and seas. This oceanography course covers many aspects associated with other disciplines including physical geography, geology (including earth history and astronomy), chemistry, meteorology, biology and ecology. Perhaps most important, human interactions, include general history, exploration, exploitation, and some of the many environmental factors affecting our modern global civilization.

What do ocean scientists do?
* Ocean scientists study all aspects of the marine physical environment (geology, chemistry, biology).
* Oceanographers map the seafloor and work with navigation and remotely sensing ocean basin regions.
* Marine geologists study seafloor rocks and sediments.
* Marine scientists work in environmental fields: climate change, waste management, resource protection.
* Marine engineers work in construction and engineering: archeology, foundations, offshore drilling.
* Marine scientists serve in national security and are involved in public health and safety.
* Marine scientists study coastal erosion hazards, waves, currents, storms.
* Marine biologists study study all aspects of the marine food chain from microbes to megafauna.
* Marine scientist are involved in all forms of shipping, port management, and marine-related industries.
* Ocean scientists in education: schools, parks, museums, and media.

Many Federal organizations employ marine scientists. Can you name these?
Abbreviation website
NOAA www.noaa.gov
Many geologists find employment through the Federal Government's employment website: www.usajobs.gov

Many states and cities also have agencies that employ marine scientists.

For instance, in California, many marine are employed within the branches of the University of California marine research programs. Scientists are employed by the CA Department of Conservation, and are involved in all aspects of water resource management, natural hazard investigations, coastal and marine resources, mines and mineral resources, etc.

Many science teachers in public schools have degrees in geology!
USGS www.usgs.gov
FWS www.fws.gov
NPS www.nps.gov
NASA www.nasa.gov
DOA www.usda.gov
DOD www.dod.gov
DOE www.doe.gov
EPA www.epa.gov
CDC www.cdc.gov

Click on images for a larger view.
Earth from Space
Fig. 1-1. Earth is an oceans planet!
Map of the Seafloor of the world
Fig. 1-2. Map of the ocean basins of the world.
Monterey Bay
Fig. 1-3. Image of coastal and marine bathymetry and land topography of the central California region showing San Francisco Bay, Monterey Bay and Monterey Canyon offshore.

The "World Oceans"

• Oceans cover 71% of Earth’s surface.
• Oceans are interconnected (meaning that all water circulates through one "world ocean”).
• Oceans have huge size and volume (97% of Earth’s water).
The four principal oceans:
Pacific (largest and deepest), Atlantic, Indian, Arctic (smallest and shallowest)
• Plus one: Southern Ocean (or Antarctic Ocean) - extension of oceans around Antarctica below 60° South latitude

Seas are:
• Smaller than an "ocean" (or part of one), often there are "not-so-perfect" boundary designations
• Composed of seawater
• Somewhat enclosed by land (except Caspian Sea which is really is, or was, a land-locked salty lake)
• The Salton Sea in California is a land-locked internal basin like the Great Salt Lake in Utah

Selected seas (discussed in this course) include: Mediterranean Sea, Adriatic Sea, Black Sea, South China Sea, Red Sea, Dead Sea, Persian Gulf, Caspian Sea, North Sea, Caribbean Sea, and Sargasso Sea.
Note there are many other "seas!" (See: "List of Seas" [Wikipedia]).



Map of world oceans and Seas
Fig. 1-4. Map of World Oceans and Seas
Ocean Data - Depth and Surface Area
Fig. 1-5. Oceans depth and surface area compared with land.

Comparison of Ocean Basins and Continents

• Average depth about 3688 m (12,100 ft)
• Deepest ocean: Pacific Ocean - Mariana Trench 11,022 m (36,161 ft)
• Average elevation of continents: 840 m (2,756 ft)
• Highest mountain: Mt. Everest 8850 m (29,935 ft)

See: "Volumes of the World's Oceans" (NOAA)


Topography is the measurement of the elevation on land. Bathymetry is the measurement of depth of water in oceans, seas, or lakes. Both topography and bathymetry are measure relative to the global average of sea level.

Early Exploration of the Oceans

Ancient World Explorations: Ancient cultures that traveled the oceans for exploration, trade and conquest:

* Shipbuilding was known to the Ancient Egyptians as early as 3000 BC. Reed boats on the Nile River as early as 4,000 BC.
* Minoan seafaring culture centered on the Island of Crete and other islands in the western Mediterranean region (2600 to 1400 BC)
* Chinese exploration began as early as 3000-2500 BC, some by ship. China's maritime economic development began in the Zhou Period (1030-221 BC).
* Mayans traveled by boat in the Caribbean region ( 800 B.C-1521 AD)
See "Tools of Navigation; Exploration Through the Ages" (NOAA)

Pacific islanders
• Navigated many remote islands in Micronesia, Polynesia, and Melanesia dating back 1000s of years
• Hawaii was inhabited around 500 AD explored from Marquesa Islands (inhabited around 300 AD)
(See: "History of Oceania" [Wikipedia] )

The Middle Ages
• Vikings explored the North Atlantic Ocean
• Colonized Greenland and Iceland
(See: "Norse Colonization of North America" [Wikipedia]) Early European navigators
• Explored the Mediterranean Sea
• Developed a method to determine latitude

Age of Discovery (1492-1522)
• Journeys to the "New World"
• Searching for new Eastern trade routes by sea
Christopher Columbus made landfall in the Caribbean Sea in 1492 (He never set foot on North America.)
Ferdinand Magellan's ship crew was first to circumnavigate the globe 1519. (Magellan didn't survived the journey, he was killed during a tribal skirmish on Mactan Island in the Philippines.)

See: "Age of Discover" (Wikipedia)
See: "Exploration of the Pacific" (Wikipedia)

Voyaging for science (1768-1780):
• English Captain James Cook (Wikipedia)
• Explored and traveled through all oceans on 3 different voyages
• Determined outline of the Pacific Ocean on 3rd voyage
• Modified shipboard diet to eliminate scurvy
• Used John Harrison’s chronometer to determine longitude (Wikipedia)

Eqyptian ship using a sounding pole to measure water depth.
Fig. 1-6. An Egyptian ship.
Leif_Ericsoon on a Viking Voyage
Fig. 1-7. Leif Ericsson on a Viking exploration voyage
Ben Franklin's map of the Gulf Stream
Fig. 1-8. Map of the Atlantic Gulf Stream compiled by Ben Franklin, published in 1769 is an example of early oceanographic research. Ponce de Leon first observed the Gulf Stream in 1513. Ben Franklin first charted the Gulf Stream with the help of a Nantucket sea captain.
View of a whale fishery from  Captain Cook's voyage
Fig. 1-9. "View of a Whale Fishery" from Captain Cook's voyage journal, 1790.

Essential Science Review Concepts for Oceanography

The Scientific Method:
• How scientific ideas are tested and validated
• Collection of data and observations leads to multiple educated guesses (hypotheses)
• Each hypothesis is rigorously tested and it fails or passes and become a Theory
• Tests/experiments must be reproducible

Define science, observation, hypothesis, fact, theory, scientific law, and scientific methods.

Science
is the systematic knowledge of the physical or material world gained through observation and experimentation. The overall goal of science is to discover underlying patterns in the natural world. The fundamental assumption of science—"the natural world behaves in a consistent and predictable manner."

The scientific method is the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to demonstrate the truth or falseness of the hypothesis, and a conclusion that validates or modifies the hypothesis.

Observation is the act of noting and recording something, such as a phenomenon, with instruments, in order to gain information.

A hypothesis is a tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.

A fact is knowledge or information based on real occurrences; something demonstrated to exist or known to have existed.

A theoryis a set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena. (A theory is also defined as an assumption based on limited information or knowledge.)

Scientific Method (steps in a cycle)
Fig. 1-10. The Scientific Method involves an ongoing cycle of inquiry.
NOAA research vessel
Fig. 1-11. NOAA research ship, the Ronald H. Brown, illustrates one of perhaps hundreds of vessels around the world involved in marine research and investigations.
 
Try out the Scientific Method! (A very valuable start to a college course!)

Example:
Use the scientific method to evaluate the data on this table comparing two variable factors: student attendance (number of classes missed in an introductory geology class) compared with final grades of students in three classes. Discuss observations, facts, hypotheses, and theories. How can these hypotheses be tested? What other factors not listed might explain observable facts?

What would it take to make these hypotheses into a proven theory?
Data: Grades vs. Attendance
Fig. 1-12. Data: Attendance vs. Grade

Essential Chemistry and Physics Concepts for Oceanography

Basic concepts of chemistry are essential to understanding the physical and chemical properties of earth materials ( rocks, seawater, organic matter, etc.). The chemical characteristics of earth materials are reflect the environments how and where they are formed, they also determine their potential fate when exposed to chemical changes. For instance, rocks formed deep underground may not be stable in the surface environment where they are exposed to water, air, temperature changes, and other physical and chemical conditions.

Aspect of chemistry and physics are discussed in nearly every chapter on oceanography. Below are highlights:


Basic chemistry concepts needed to be understood for this course include:
* All matter is made up of atoms, and atoms are made up of atomic particles (electrons, protons, and neutrons. An atom is the smallest unit of a chemical element and consists of a nucleus, which has a positive charge, and a set of electrons that move around the nucleus (composed of neutrons & protons).
* A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, nitrogen, and oxygen.
* An element is a substance that cannot be broken down into simpler substances by chemical means.
* An element is composed of atoms that have the same atomic number, that is, each atom has the same number of protons in its nucleus as all other atoms of that element.
* The Periodic Table is a list of known chemical elements arranged in order from smallest to largest and by group chemical properties. It is a list of 108 known elements arrange by atomic number. Of these, 92 are naturally occurring (prior to development of artificial nuclear research and development). The lightest element, hydrogen, has one proton, whereas the heaviest naturally occurring element, uranium, has 92 protons.
* Atoms bond together to form molecules. A molecule is a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
* A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. All minerals are chemical compounds, but by comparison relatively few compounds are naturally occurring minerals!
* Types of molecular bonds include metallic (for metals), ionic (compounds that dissolve easily), covalent (most others).
* A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. Examples of mixtures include rocks, magma (molten rock) air, and seawater.
* Chemical formulas are used to describe compounds such as H2O (for water), NaCl (for salt), CO2 (for carbon dioxide)

The most abundant elements in our physical environment are: H, C, N, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Fe

These elements are:
* ingredients of common rocks and sediments (solids)
* components of seawater and air (liquids & gases)
* essential nutrients for life (organic compounds)

An atom of lithium is composed of a nucleus with 3 protons and several nuetron, and surrounded by a cloud of 3 spinning electrons
Fig. 1-13. Structure of an atom: this example is the element lithium composed of a nucleus of 3 protons, 4 neutrons, and an outer shell of 3 electrons spinning around the nucleus.
Periodic table highlighting elements most essential for life
Fig 1-14. The periodic table with essential elements highlighted.
Composition of the crust
Fig. 1-15. Composition of the crust. Rock samples collected from around the world show that the chemical composition of the Earth's crust is not uniform, but certain elements are much more abundant than others. Silicon and oxygen are the two most abundant elements in the crust.

Chemical Bonds

Molecular compounds are held together on an atomic level by chemical bonds. Three types of chemical bonds include ionic bonds, metallic bonds, and covalent bonds. The types of chemical bond influence the physical properties of the molecular compounds they form.

Molecular compounds held together by ionic bonds are salts. Salts readily precipitate from and dissolve in water. Natural salts like halite (NaCl) and gypsum (CaSO4) are soft minerals (not suitable for gems because they scratch or fracture easily, and can dissolve in water.

Metals are held together by metallic bonds. Compounds with metallic bonds transmit electricity. Metalloids are intermediate between those of metals and solid nonmetals. Although most elements are metals (all those on the left and center parts of the Periodic Table), only a few elements occur naturally in metallic form including gold, platinum, copper, iron, and mercury (in liquid form). Some minerals are metalloid compounds including pyrite (FeS2), magnetite (Fe3O4), and galena (PbS).

Molecular compounds held together by covalent bonds are non-metallic compounds. These materials can form crystal complexes and do not transmit electricity and tend to be durable compounds. Most gems are non-metallic compounds. The mineral quartz (SiO2) is a non-metallic crystalline compound (see Figure 1-19).

Van der Waals forces (bonds) are weak, nonspecific forces between molecules and include attractions and repulsions between atoms, molecules, and surfaces. Van der Waals forces are responsible for “friction” and what makes water “sticky.”


Salt dissolves in and precipitates from water Salt deposits in Death Valley
Fig. 1-16. Salt crystals are held together by ionic bonds. Salt compounds dissolve in and precipitate from water. Fig. 1-17. This view shows salt crystals precipitating on a dry lakebed in Death Valley, California.
Metals (native copper and gold), magnetite and pyrite Quartz crystal
Fig. 1-18. Metallic bonds occur in metallic minerals (like native copper and gold) and metalloid minerals (like magnetite and pyrite). Fig. 1-19. Most minerals are non-metallic crystalline compounds held together by covalent bonds (and will not transmit electricity). [Quartz]
   

Isotopes (and Radionuclides)

Many elements have one or more isotopes. Isotopes are each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties. Some isotopes are not stable and ultimately break down or change in other elements. In this case, the isotope is considered a radioactive form of an element. Many elements have both stable and radioactive isotopes. For example, the element carbon has 3 isotopes: 12C and 13C are stable, whereas 14C is unstable and will undergo radioactive decay. All there isotopes have 6 protons, but have 6, 7, and 8 neutrons, respectively.

In "nature," there are 80 different elements that have one or more nuclides. Of these, at least 254 stable isotopes that have never been observed to decay. Another 50 are radionuclides (unstable isotopes that undergo radioactive decay). With the invention of nuclear weapons, and the numerous nuclear bomb test through the 1950s to the present, there are now many more radionuclides loose in the environment.

For example, the March 2011 Fukushima Daiichi nuclear disaster associated with the massive earthquake and tsunami in Japan released large amounts of radiation into the marine environment.

Radioactivity measured with a geiger counter
Fig. 1-20. Radioactive elements that occur in rocks and minerals include potassium, thorium, radium, and uranium. and may display measurable radioactivity. A geiger counter us used to measure materials for radioactivity.

Energy

Energy exists in several forms such as heat, kinetic energy (mechanical), light, potential energy, electrical, or other forms. All physical and chemical reactions involve either the loss or gain of some form of energy.

Electromagnetic energy
from the sun it the force behind all motion of the atmosphere and the oceans.
Geothermal energy
is the driving force for motion within the planet (including plate tectonics, earthquakes, and volcanoes). Both solar electromagnetic energy and geothermal energy are utilized to support life and ecosystems within the marine environment.

All natural materials either transmit, reflect, or absorb electromagnetic energy in different ways. Solar energy that is absorbed by the atmosphere, oceans, and land is converted to heat or other energy forms. An equivalent amount of energy is radiated back into space. Some of the energy is used to move the oceans and atmosphere, and support life in the process over time.

The electromagnetic spectrum
Fig 1-21. The electromagnetic spectrum is the range of wavelengths or frequencies over which electromagnetic radiation extends.
 

Gravity, Mass, and Density

Gravity is the weak force that attracts a body toward the center of the earth, or toward any other physical body having mass.

Mass
is the property of matter that measures its resistance to acceleration. Roughly, the mass of an object is a measure of the number of atoms in it. Gravity is the force that holds Earth in orbit around the Sun, and the Moon in orbit around the Earth.

Density is the ratio between mass and volume. It is a measure of how much matter an object has in a unit volume (such as cubic meter or cubic centimeter).

Density = mass/volume
• Usually defined in grams per cubic centimeter - gm/cc

Density Stratification
• The earth and oceans have layers based upon density differences, they are density stratified.

Examples of the density of earth materials
:
• Air ~0.1 gm/cc
• Freshwater 1.0 gm/cc
• Saltwater ~1.001-1.03 gm/cc
• Surface rocks ~3 gm/cc
• Center of earth ~16 gm/cc

Calculate the change in density when we add 1% salt to freshwater:

(.99)(1.0 gm/cc) + (0.01)(3.0 gm/cc) = 1.02 gm/cc
Seawater has an average density of 1.027 gm/cm3, but this varies with temperature and salinity over a range of about 1.020 to 1.029.

The Rock Cycle

The “rock cycle” is a conceptual model of how earth materials form and change in the earth’s crust over time. The rock cycle represents the series of events in which a rock of one type is converted to one or more other types and then back to the original type. Both products (rocks and sediments) and processes (such as melting, cooling, erosion, deposition, metamorphism, remelting) are part of this idealized cycle. The passage of geologic time is the essential component, although some processes are much faster than others. Note that all these types of processes are taking place simultaneously, but at different locations on and within the crust. It is important to note that "rock cycle" processes occur on other "rocky planets or moons" but rates may vary due to the presence (or lack of) atmospheric gases or fluids (including water) or availability of heat enough to melt rocks.
The Rock Cycle
Fig. 1-22. The Rock Cycle is a conceptual model that portrays "processes and products" changing over time

General Classification of Solid Earth Materials

Igneous rocks are rock formed from molten materials. These includes intrusive rocks (rocks cooled from molten material [magma] below the surface) and extrusive rocks formed on the Earth's surface by volcanism.

Sediments are solid fragments of inorganic or organic material that come from the weathering of rock and soil erosion, and are carried and deposited by wind, water, or ice.

Sedimentary rock
s are rocks that formed through the deposition and solidification of sediment, especially sediment transported by water (rivers, lakes, and oceans), ice ( glaciers), and wind. Sedimentary rocks are often deposited in layers, and frequently contain fossils.

Metamorphic rocks are rocks that were once one form of rock but has changed to another under the influence of heat, pressure, or fluids without passing through a liquid phase (melting).

Igneous Rocks

• The term "igneous" applies to rocks or minerals that have solidified from molten material.
• Molten material underground is call magma; when it erupts and flows on the surface it is called lava.
* When molten material cools, it crystallizes into rock.
• When magma "intrudes" other rocks underground and cools it forms intrusive igneous rocks (examples include granite, diorite, and gabbro). Slower cooling times underground result in bigger mineral crystals.
• Lava that extrudes on the surface as a volcanic eruption cools quickly, forming extrusive igneous rocks (examples include rhyolite, andesite, and basalt).

Examples:
Volcanic (extrusive): Hawaii (basalt) and (Cascades) andesite
Plutonic (intrusive): Sierra Nevada (granites)
Intrusive igneous rocks: granite, diorite, gabbro Extrusive igneous rocks: rhyolite, andesite, basalt Igneous provinces
Fig. 1-23. Intrusive (plutonic) igneous rocks Fig. 1-24. Extrusive (volcanic) igneous rocks. Fig. 1-25. Igneous regions of the world.
Basalt volcanic eruption Mount St. Helens is an andesite volcano Yosemite granites
Fig. 1-26. Basalt volcano: Pu'u'o'o volcano on Hawaii's Big Island. Fig. 1-27. Andesite volcano: Mount St. Helens in the Cascade Range, WA. Fig. 1-28. Granites exposed in core of Sierra Nevada Range.

Sediments and Sedimentary Rocks

Sediments are solid material that has settled from a state of suspension in a fluid (water, ice, or wind).
• When lithified (consolidated or cemented) becomes a sedimentary rock.
• Sediments are derived from weathering and erosion of pre-existing rocks
• Sediments and sedimentary rocks can help tell the geologic history of an area.
• Classified by grain size and source
• Sedimentary rocks may contain fossils

Examples: conglomerate, sandstone, shale, limestone, gypsum, and marl
Sedimentary Rocks
Fig. 1-29. Common sedimentary rocks

Metamorphic Rocks

• Formed by “changing” pre-existing igneous, sedimentary or other metamorphic rocks.
* Metamorphic processes involve changes caused by exposure to heat, pressure, and chemicall-active fluids.
• Driving forces are increased heat and pressure as rocks are buried deep into the earth in association with mountain-building periods.
• Typically develop a fabric or texture that differentiates it from the original rock it formed from (called a "protolith").
• Commonly found in ancient crustal rocks exposed in mountain ranges and in the core of continental landmasses.

Examples: quartzite, slate, marble, gneiss, schist, and serpentinite (the State Rock of California)
Metamorphic Rocks
Fig. 1-30. Common metamorphic rocks

Zones of the Earth Climate System

The “tropics” are the region of the world between the parallels of latitude 23°26ʹ north (Tropic of Cancer) and 23°26ʹ south (Tropic of Capricorn) on opposite sides of the equator (0°). These lines of latitude each of two corresponding circles on the celestial sphere where the sun appears to turn after reaching its greatest declination, marking the northern and southern limits of the ecliptic.

The term "polar" is used to describe the high latitude cold regions surrounding the earth's north and south poles. The Arctic Circle runs 66°34′ north of the Equator. North of this line is the North Frigid Zone (also known as “Land of the Midnight Sun” where the sun never sets on the summer solstice). The Antarctic Circle is parallel of latitude approximately 66°34′ south and defines the northern boundary of the South Frigid Zone. The Antarctic Circle marks the approximate limit south of which the sun remains above the horizon all day on the summer solstice.

The regions between the tropics and the polar regions are called the "Temperate" (North Temperate Zone and South Temperate Zone).



Globe showing location of tropics, temperate zones, and polar zones
Fig. 1-31. Location of tropics, temperate, and polar zones.
 

Understanding Maps

Maps are perhaps the most important tools for navigation and evaluating features on the land's surface, underwater, or underground for a host of issues involving land use and natural resources. Maps have been used by back into prehistoric times. However, the evolution of maps in the modern digital world has changed map making—enhancing their use in nearly all aspects of modern science, technology, and culture. Modern maps are created with "geographic information systems (GIS)"—computer-based map-generating programs can combine geographic (spatial) information with many kinds of databases (medical, commercial, civic infrastructure, biological, satellite data, etc.). Satellite data is increasingly used for nearly all aspects of mapping of all the "spheres" described above.
Map of Human Migration
Fig. 1-32. Maps show "thematic information" in a geographic context.
Relief means relates to height and shape characteristics of a landscape (such as high relief, low, relief, gentle relief, rugged relief, etc. Shaded-relief maps show changes in elevation (topography and bathymetry) using shades of gray or color.

What are Latitude and Longitude?

Locations on the Earth's surface are defined using latitude and longitude coordinate system.

Latitude is the angular distance of a place north or south of the earth's equator, usually expressed in degrees and minutes. Lines of latitude are called parallels. Latitude lines parallel the Equator. Each degree of latitude is approximately 69 miles (111 kilometers) apart. Latitude is easy to find at sea by sighting the North Star in the Northern Hemisphere and determining the angle of the star above the horizon (subtract it from 90°).

Longitude
is the angular distance of a place east or west of the Prime Meridian usually expressed in degrees and minutes. In order to make an accurate map of the stars for use in ship navigation, in 1884, a location indicating the precise location of 0° East-West was designated in the cross hairs of a telescope in the Royal Observatory (now located on the grounds of the National Maritime Museum) in Greenwich England. This line marks the reference location of the Prime Meridian now used in all global mapping (including GPS location systems). The International Date Line is on the opposite side of the earth located 180° east or west of the Prime Meridian.

A meridian is a circle of constant longitude passing through a given place on the earth's surface and the terrestrial poles. Longitude lines (of equal spacing measured in degrees) are widely spaced at the equator but converge at point at the North and South Poles. The Prime Meridian is designated 0° (zero degrees). Meridian lines east of the Prime Meridian are designated positive values (0° to 180° east); whereas meridian lines west of the Prime Meridian are designated negative values (-0° to -180°). At 180° east or west is the International Date Line. A degree of longitude is widest at the equator at 69.172 miles (111.321) and gradually shrinks to zero at the poles. At 40° north or south the distance between a degree of longitude is 53 miles (85 km).

Defining locations with a latitude-longitude coordinate system
—any location on the planet surface can be defined by a number in degrees, minutes, and seconds north or south of the Equator and east or west of the Prime Meridian. (Compare to hours, minutes, seconds on a clock!)

Example: Location of the Statue of Liberty in New York Harbor

The standard coordinates of the are:
Latitude: 40°68′92"N
Longitude: 74°04′ 45"W.

Described in decimal degrees the coordinates of the Statue of Liberty are: Latitude:40.689758°
Longitude:-74.045138°

San Diego
is generally located around 32.7150° N, 117.1625° W
Globe view of Earth from space
A globe view is the only way to have perfect map projection!

Find the latitude and longitude of any named location or landscape feature on the GeoNames website.

The earth is round (a sphere like a globe) but maps are flat. As a result, maps that show large regions are distorted. Map projections are attempts to portray a portion of the earth on a flat surface. The flattening of a map always causes some distortions of distance, direction, scale, and area. Large scale maps (such as a map of a continent or a world show much distortion, however, maps on small scales (such as a map of a town or neighborhood) have relatively little distortion. There are many map projection systems, each serves different purposes and has some variety of distortion. Learn more about map projections at the U.S. Geological Survey's Map Projections website.



Global Positioning System (GPS)—a space-based global navigation satellite system that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites. (See GPS on Wikipedia)
Global projection
Fig. 1-33. Longitude and Latitude projected on a globe
Mercator Map
Fig. 1-34. Map of the world showing latitude and longitude in a Mercator (flat) projection
Map of world, Mercator Projection
Fig. 1-35. Map of world showing with Mercator Projection - notice distortion in high latitudes because longitude lines are not converging
Map of North America Lambert Projection
Fig. 1-36. Map of North America with Lambert Conic Projection - on this scale distortion of America is minimal, but look at South America.
Satellite network of the Global Positioning System
Fig. 1-37. Satellite network of the Global Positioning System.

Geologic Time Scale

Geological time refers to the time of the physical formation and development of the Earth (especially prior to human history). Geologic time also applies to the age and history of the Universe. Geologists have subdivided periods in Earth's history is measured periods spanning millions of years (Ma). The Geologic Time Scale has been established to name segments of time periods to help define the chronology of events (such as mountain range formation), the formation of rock units (such as the age of a lava flow), the age of fossils, organizing geologic map units, and other purposes. Figure 2-1 is a standard geologic time scale listing names of major time periods with time span information. Names of geologic time periods (like "Late Cretaceous" or "Pleistocene") are used for organizing geologic map units, charting the age or petroleum-bearing rock layers underground, and perhaps hundreds of other purposes.

College courses in historical geology examine what is currently known about the age of the Earth and the events as they are known or inferred to have occurred. For this course, the name of geologic time periods are used to explain the age of when rocks or sedimentary deposits formed, and where and how they occur in relation to other rocks and deposits associated with them. For example, rock layers containing dinosaur bones will correlate to the specific time period that the dinosaurs lived in the geologic past.

Every rock has a history! The geologic time scale used today has evolved through the past two centuries as new scientific discoveries have been made and new technologies for dating the age of earth materials have become available. The most recent version of the geologic time scale is released by the Geological Society of America as updated versions become available.

Note that the notions that the Earth being "old" (measured in billions of years) has not been all that popular with some fundamentalist religious groups throughout the ages, but even religious organizations evolve over time. The primary arguments about the age of the Earth and the observable universe have been resolved by the global scientific community, but paradigms have ways of shifting as new discoveries are made and new information becomes available, and those ideas are tested by scientific methods. Vast periods of time in earth history are fundamental parts of understanding biological evolution of life on earth (paleontology), understanding genetics, particularly related to human evolution, and in astronomy explaining the vastness and age of the observable universe.

Fossils are traces or remains of prehistoric life now preserved in rock.
Paleontology: study of fossils
• Fossils are mostly found in sedimentary rocks
• Where found, fossils aid in interpretation of the geologic, geographic, and environmental past
• Fossils serve as important time indicators
• Fossils allow for correlation of rocks from different places
Geologic Time Scale
Fig. 1-38. Geologic Time Scale showing major geologic events in Earth history and the evolution of life on earth. New scientific discoveries are refining knowledge about the chronology and impacts or significance of events through deep Earth time.
Time Scale Clock
Fig. 1-39. "If a second were 100,000 years" - this classic diagram shows the distribution of different ages of time as if it were all squeezed into a 24 hour day. All of human history would fit in the last fraction of a second!
Earth's Place in the Universe
* The Moon revolves around the Earth every 27.32 days.
* The Earth-Moon System revolves around the sun every 365.242 days (1 year)
* It takes the Sun about 230 million years to make one complete orbit around the center of our Milky Way Galaxy (traveling about 828,000 km/hr).Our galaxy is about 100,000 to 120,000 light-years in diameter and contains over 200 billion stars. Our Solar System resides roughly 27,000 light-years away from the Galactic Center;
Read about the Observable Universe (Wikipedia)
Observable Universe
Fig. 1-40. Earth's place in the Universe.
The Big Bang Theory is a cosmological theory holding that the Observable Universe originated approximately 13.8 billion years ago from the violent explosion of a very small agglomeration of material of extremely high density and temperature. See a NASA website about the Big Bang Theory. Early in the history of the Universe matter began to condense and with time gravitation attraction pulled materials together to for galaxies.

A galaxy is a system of millions to many billions of stars, together with gas and dust, held together by gravitational attraction. Earth is in the Milky Way galaxy. See a NASA website about Galaxies.

A star is a self-luminous celestial body consisting of a mass of gas held together by its own gravity in which the energy generated by nuclear reactions in the interior is balanced by the outflow of energy to the surface, and the inward-directed gravitational forces are balanced by the outward-directed gas and radiation pressures. Our sun is our star in the center of our solar system. See a NASA website about Life Cycle of Stars.

A nebula is an interstellar cloud within a galaxy consisting of gas and dust, typically glowing from radiant energy from stars nearby within them. Nebulas are the birth place of stars and solar systems. Nebulas can form from the explosion of stars at the end of their life cycle.

The solar system is the system containing the Sun and the bodies held in its gravitational field, including the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto), planetary moon, the asteroids, and comets, and other interstellar matter. See NASA websites about Planets and Moons within the Solar System and Earth's Moon. (images below from NASA).

Studies of meteorites and samples from the moon suggest that the Sun and our solar system (including proto-planets) condensed and formed in a nebula about 5 billion years ago. Currently, the oldest samples of "Early Earth" rock samples from the Jack Hills region of Australia that contain crystals of the mineral zircon dated to an age of about 4.4 billion years. A recent Scientific American article places the current assume age of the earth is 4.55 billion years old.

Brief story of the Big Bang Galaxy
Fig. 1-41. A very brief story of the Big Bang and the evolution of the Observable Universe over ~13.8 billion years Fig. 1-42. A spiral galaxy: a typical galaxy may have hundreds of millions of stars
Galaxies Sun
Fig. 1-43. Deep-space observing telescopes show distant field of galaxies: galaxies can be seen in all directions in distant space. The distance to these objects are in the range of thousands to billions of light years away. Fig. 1-44. The Sun (our star), is one of billions of stars in our Milky Way Galaxy. There are many types of stars and other objects ranging from dust and gas clouds to super massive objects called Black Holes.

Evolution of the Earth in Space

Ancient supernova explosions in the distant past produced the elements we observe in our solar system today.
• Nuclear fusion in stars coverts hydrogen into helium and elements up to iron.
* Elements heavier than iron are created by supernova explosions.
* Gas and dust from supernova explosions become part of nebulas.
* Gravity condenses material in nebulas into new star system.

Nebular hypothesis of the origin of the Solar System

• Assumes a flat, disk shape with the proto sun (pre-sun) at the center.
• Inner planets begin to form from metallic and rocky substances (dust).
• Larger outer planets began forming from fragments of ice (H2O, CO2, and others).



Proto-earth formed
• Initially homogenous
• Larger in size than today’s Earth
• No continents or oceans, or life



Formation of Earth’s layered structure

• Denser metals sank to the center
• Early crust began to form
• Chemical segregation established the basic divisions of Earth’s interior


Formation of the Earth-Moon System

Studies of the rocks brought back from the Apollo Missions show that the Earth and Moon have similar mineral compositions. This, and the fact that the Earth has a tilted axis, and the moon's orbit is not in the ecliptic plane, suggest that the moon may have formed from the collision of another small planet-sized object early in the history of the Solar System.
Subernava Nebula
Fig. 1-45. Supernovas are great explosions that partial to complete demolish aging stars, releasing new matter and gas to create a new generation of stars Fig. 1-46. Nebula, the birthplace of stars; some are formed from the explosion of other more ancient stars, some thousands to millions time larger than the Sun.
Nebula Carena Our Solar System
Fig. 1-47. Carina Nebula, a part of our Milky Way Galaxy where new stars are forming and emerging from a gas and dust cloud "stellar nursery." Fig. 1-48. Our Solar System originated from gas, dust, and other matter that gravity pulled together in a stellar nebula about 5 billion years ago.
   
Volcanic Outgassing
• Large volumes of water/carbon dioxide formed earths primitive atmosphere
• Earth's primitive atmosphere: carbon dioxide, nitrogen, methane, and ammonia.


* By about 4 billion years ago (BYA) the earth's oceans were essentially in place. Oldest rocks from Canada are of this age.

Evolution of the Atmosphere - the gateway to modern life forms.
* By about 1.5 BYA Oxygen production greatly accelerated from green plants.
* By about 1 BYA First multi-cellular organisms appear.
• Advanced life proliferates starting about 540 Million years ago (MYA) as Phanerozoic Time begins: Paleozoic, Mesozoic, and Cenozoic Eras.
Earth collides with another planetessimal, forming the Earth Moon system. Andromeda Galaxy, 2.5 million light years away is visible to the nake eye on autumn nights
Fig. 1-49. Proto Earth colliding with another object Fig. 1-50. Andromeda Galaxy is visible to the naked eye on autumn nights.

Planets and Other Objects in our Solar System

Mercury Venus Earth Mars
Fig. 1-51. Mercury - rocky planet, no moons, no atmosphere Fig. 1-52. Venus - rocky planet with hot atmosphere, no moons Fig. 1-53. Earth - rocky planet with oceans, atmosphere, life!, and one moon Fig. 1-54. Mars - rocky planet with ice caps at poles, thin atmosphere, 2 small moons
Jupiter Saturn Uranus Neptune
Fig. 1-55. Jupiter - largest of the gas planets, has 67 moons, of which 4 are large Fig. 1-56. Saturn - a gas planet famous for its visible rings. Currently has 62 moons, including Titan, the largest in the solar system. Fig. 1-57. Uranus - another large gas planet with 5 medium-sized moons (many smaller ones too) Fig. 1-58. Neptune - the largest, outermost gas planet, has 13 known moons
Pluto Moon Asteroids
Fig. 1-61. Asteroids are solid objects in space consisting mostly of rock, dust, some metals, and possibly ice. Most asteroids orbit the sun in the Asteroid Belt located between Mars and Jupiter.
Comet Haley
Fig. 1-62. Comets are like asteroids (mostly frozen gases and ice, dust, some rocky material) that leave a trail of material as they are heated as they approach the sun. There may be more than 100 million comets in the outer Solar System.
Fig. 1-59. Pluto - "formerly a planet," now it is called a "planetesimal," a "dwarf planet." There are 7 planetary moons larger than Pluto. Fig. 1-60. Earth's Moon - one of the largest of at least 168 moons orbiting planets. Jupiter has the most: 67, only 4 are large.
asteroid—any of the thousands of small irregularly shaped bodies of stone, metal, and ice that revolve about the sun. In our solar system, asteroids typically range in size from about one-mile (1.6 km) to about 480 miles (775 km) in diameter. Most asteroids lie in in orbits between those of Mars and Jupiter, however many large objects have been observed passing through Earth's orbital path. Asteroid collisions with earth were frequent in Earth's early history, but are now extremely rare events. The extinction of the dinosaurs and many other species is mostly blamed on the environmental catastrophe created by an asteroid impact about 65 million years ago, defining the end of the Cretaceous Period (and Mesozoic Era). See a NASA website about asteroids.

comet
—a celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water. See a NASA website about comets.

meteor—a bright trail or streak that appears in the sky when a meteoroid is heated to incandescence by friction with the earth's atmosphere.

meteorite—a stony or metallic mass of matter that has fallen to the Earth's surface from outer space. See a NASA website about meteors and meteorites.
Meteorite with magnet
Fig. 1-63. An iron-nickel meteorite is magnetic.
 
A bollide is a large meteor (or asteroid or comet) that explodes in the atmosphere. A recent bollide explosion involved the Chelyabinsk meteor that blew up over Russia on February 15, 2013. The explosion occurred high in the atmosphere, but the atmospheric shock wave blew out windows, doors, and injured over a thousand people on the ground (see YouTube video). See a NASA website about bollides.

An atrobleme is an eroded remnant of a large crater made by the impact of a comet or asteroid (large meteorite).
Bollide over Oklahoma Panhandle, 9/30/2008 Bollide events during period 1994 to 2013
So... Can you explain why are there so many craters on the surface of the moon but not on surface of the earth? Fig. 1-64. Bollide (meteor fireball) over Oklahoma Panhandle, 9/30 2008 Fig. 1-65. Map of reported bollide events 1994-2013.

Water and Oceans On Other Planets and Moons

Water is known to exist throughout the solar system and beyond. However, liquid water is only known on the surface of planet Earth where surface temperatures and atmospheric pressures are in the range where it can remain fluid. Tidal forces between planets and their moons provide a source of energy to keep water in liquid form below the surface of some of the moons in the Solar System.
Both Venus and Mars likely had liquid water oceans early in the evolution of the Solar System, but now Venus is too hot for water to exist, and Mars is too cold and its atmosphere is too thin. Exploration of Mars suggests that liquid water may exist underground and traces may locally flow on the surface, causing erosion, where conditions are right.
Europa: Exploration of the Jupiter planetary system suggest that its moon, Europa has an outer crust of solid ice about 10–30 km (6–19 mi) thick which overlies a liquid ocean thought to be about 100 km (60 mi) deep. The volume of water in this subterranean ocean is estimated to be more than two times the volume of Earth's oceans!
Ganymede: A subsurface saline ocean is also theorized to exist on Jupiter’s moon Ganymede. Its ocean is estimated to be 100 km deep and lies beneath a crust of ice estimated to be about 150 km thick.

Enceladus: Saturn’s moon, Enceladus, is also believed to have a subsurface ocean and NASA’s Cassini spacecraft observed geysers of water erupting from Saturn’s moon, Enceladus during its exploration of the planet system. Spectrographic observations of the geysers also contained traces of salt, carbon dioxide, nitrogen, and hydrocarbons. The moon also has liquid water oceans below its surface, and the geysers appear to be driven by tidal forces between the moon and Saturn.
Water planets outside the Solar System: In recent years, astronomers working with powerful telescopes have been finding planets orbiting other stars within our "galactic neighborhood." Although most of these planets are larger than our Earth, some of the planets display evidence of water, possibly oceans.
Venus and Mars
Europa
Gamymede
Enceladus
Fig. 1-66. Venus and Mars Fig. 1-67. Europa Fig. 1-68. Ganymede Fig. 1-69. Enceladus
See "Extraterrestrial liquid water" (Wikipedia)

Basic Geologic Principles

Uniformitarianism

Uniformitarianism is the theory that all geologic phenomena may be explained as the result of existing forces having operated uniformly from the origin of the earth to the present time. Uniformitarianism is commonly summarized: "The present is key to the past."

A Scottish physician, James Hutton (1726-1797) studied rocks and landscapes throughout the British Isles and promoted "uniformitarianism." Hutton fearlessly debated that the Earth was very old, measured in millions of years rather than thousands of years as promoted by the religion organizations of his times. Many scientists of his time promoted a theory of catastrophism.

Catastrophism is the theory that major changes in the earth's crust result from catastrophes rather than evolutionary processes. The theory of catastrophism was more in line with religious doctrine common in the 17th and 18th centuries.

It is interesting that today, uniformitarianism still applies to most geologic and landscape features, but discoveries have show that the Earth, or large regions of it, have experience great "catastrophes," such as asteroid impacts, great earthquakes, collapse of continental shelves (causing massive underwater landslides and tsunamis), super storms, great floods, or volcanic events. However, these events can be scientifically viewed within the greater context of modern geology. Uniformitarianism explains how observable processes taking place over long periods of time can change the landscape. Examples include:

* earthquakes only happen occasionally, but in an area taking place over millions of years can result in the formation of a mountain range.
* the deposition of silt from annual floods over millions of years can built a great river delta complex.
* the slow growth and accumulation of coral and algal material over time can build a great barrier reef.

Rock Formations

Stratigraphy is abranch of geology concerned with the systematic study of bedded rock layers and their relations in time and the study of fossils and their locations in a sequence of bedded rocks. A stratum is a bed or layer of sedimentary rock having approximately the same composition throughout (plural is strata).

James Hutton also contributed to a theory of "rock formations." A rock formation is the primary unit of stratigraphy, consisting of a succession of strata useful for mapping or description. A rock formation typical consists of a unique lithology (rock type) that has a relatively defined geologic age and is considered "mapable" (occurs throughout area or region, both on the surface and in the subsurface.

Rock formations preserved information about what conditions were like when the original sediments were deposited, such as on a river delta, a coastal beach environment, a ocean setting, or a massive dune field. Rock formations can also consist of igneous rocks, such as ancient lava flows or massive volcanic ash deposits. Rock formations typically represent materials that accumulated over period of hundreds of thousands, to many millions of years.

Stratum exposed along a shoreline (Anderson Reservoir, Morgan Hill, CA) Rock formations exposed along Calvert Cliffs, Chesapeake Bay, Maryland
Fig. 1-70. Strata exposed along a reservoir shoreline. Each layer represents sediments deposited under unique environmental conditions over a period of time (days, years, centuries). Fig. 1-71. Layers of sedimentary rock formations of the Cenozoic Era are exposed in many locations US coastlines. These are Calvert Cliffs on Chesapeake Bay, Maryland.
   

Methods for determining the age of Earth materials and features

Geochronology, the branch of earth sciences concerned with determining the age of earth materials and events through geologic time.

How do geoscientists determine the age of rocks or fossils? How do they figure out how long ago and in what order did geologic processes or events take place? For instance how do they know how often a volcano erupts or how often earthquakes take place. Geologists now have many ways to determine the age of materials using absolute and relative dating methods.

Absolute and Relative Dating Methods

Absolute dating is a general term applied to a range of techniques that provide estimates of the age of objects, materials, or sites in real calendar years either directly or through a process of calibration with material of known age. There are many methods of absolute dating rocks or other ancient materials. The methods of absolute dating used depends on whether suitable samples are available for testing.

Relative dating
is the science of determining the relative order of past events, without necessarily determining their absolute age (see below).

Decay of radioactive isotopes

Unstable isotopes emit particles and energy in a process known as radioactive decay. A "parent" isotope is an unstable radioactive isotope. A "daughter" product isotope results from the decay of a parent.

Radioactive decay occurs at known rates and using this you can determine the age of certain types of rocks.

Dating of materials that contain naturally-occurring radionuclides (radioactive isotopes) is possible because the rate of decay of the radionuclides are known. The radiation decay "clock" starts the moment a mineral in a rock forms (or for 14C when an organism dies).

A "half-life"the time required for one-half (50%) of the parent to change to daughter product. The next half-life is when only a quarter of the original parent radionuclide remains, and so on. Age determinations can be determined by comparing the percentage of the radionuclides in a new "fresh" sample with the percentage in the old sample material being tested.

Commonly referenced studies of absolute dating utilize the radioactive decay of:
Parent Isotope
Daughter Isotope
Half Life
238U (unstable uranium isotope)
206PB (stable lead isotope)
~ 4.5 billion years
40K (unstable potassium isotope)
40Ar (stable argon isotope)
~ 1.25 billion years
14C (unstable carbon isotope)
14N (stable nitrogen isotope)
5,730 years
Note there are many other radionuclides used for absolute dating.

Sources of error in Absolute dating. Error can be caused by a variety of misinterpretation. Do we have a general good idea of the "geologic history" of the sample? (See Relative Dating below). Factors include:
• A "closed system" is required. (Has it been exposed to more recent processes?)
• To avoid potential problems, only fresh, unweathered rock samples should be used
• No parent or daughter is added or subtracted from the sample
• No daughter product at start
• Decay is consistent with time

(other sources of information including relative dating - see below) Not all rocks can be dated by radiometric methods
Detrital sedimentary particles are not the same age as the rock in which they formed
Metamorphic rock age may not necessarily represent the time when the rock formed
Datable materials (such as volcanic ash beds and igneous intrusions) are often used to bracket ages
• Bracketing sedimentary ages using igneous rocks

Absolute dating
Fig. 1-72. Absolute dating methods. Different isotopes are used to study different materials and geologic time ranges.
Hydrogen bomb blast in the 1950s
Fig. 1-73. Nuclear bomb testing release large quantities of radionuclides into the global environment. Atmospheric and oceanic nuclear testing began with the first test on July 16, 1945 (Trinity Site in New Mexico). Most atmospheric testing ended in 1980, but continues underground. See Nuclear Weapons Testing (Wikipedia)
 

Radiocarbon Dating

Radiocarbon dating is the most used method of absolute dating because of its "dating window" of about the past 100,000 years. 14C (isotope carbon -14) is a unstable radioactive isotope (radionuclide). Radiocarbon dating (using ratios of the isotopes of radioactive isotope14C to to stable isotopes 12C and 13C derived from buried or isolated organic or carbonate materials. The "half life" of 14C [unstable isotope carbon-14] is about 5,730 years. Radiocarbon dating has extensively used in archeological investigation and the study of climate change over the last several hundred thousand years, and precision methods now available make radiocarbon dating highly reliable. Radiocarbon dating is highly effective for extracting ages of organic materials (bone, tissues, wood, etc.) that have been isolated by burial and is effective for dating materials materials from ancient human activities going back for many thousands of years.
Radiocarbon Dating method
Fig. 1-74. The science behind the radiocarbon absolute dating method.
Relative dating is the science of determining the relative order of past events, without necessarily determining their absolute age (see above). Relative dating involved the study of fossils and the correlation or comparison of fossils of similar ages but from different regions where their age is known. Microfossils derived from sediments and cores from wells help in the subsurface exploration for oil and gas.

Relative dating
is useful and relatively easy compared with absolute dating
• Not all rocks can be dated with radioactivity (see above).
• This is the way we tell the ages of rock layers relative to each other.

Basic Geologic Principles

These basic principles are easily observed in geologic outcrops, but have value for any number of scientific and technical applications beyond geology. Figure 1-73 illustrates the three "laws" that are used in resolving the age of rocks and the order in which they formed or geologic events occurred. The three laws are as follows:

Law of Original Horizontality—this law states that most sediments, when originally formed, were generally laid down horizontally. However, many layered rocks are no longer horizontal.

Law of Superposition—this law states that in any undisturbed sequence of rocks deposited in layers, and the oldest on bottom the youngest layer is on top. Each layer being younger than the one beneath it and older than the one above it.

Law of Cross-Cutting Relationships—this law states that a body of igneous rock (an intrusion), a fault, or other geologic feature must be younger than any rock across which it cuts through.

Inclusions
• An inclusion is a piece of rock within another rock
• Rock containing the inclusion is younger

Basic geologic principles
Fig. 1-75. Basic geologic principles illustrated.
Basalt inclusion in granite
Fig.1-76. Example of a basalt inclusion in granite. The granite is younger than the basalt.

Unconformities: Gaps in the "geologic record"

Following on the Law of Original Horizontality and Law of Superposition, both Hutton and Lyell recognized erosional boundaries preserved between rock layers representing "gaps in the geologic record." They named these gaps unconformities. An unconformity is a surface between successive strata that represents a missing interval in the geologic record of time, and produced either by: a) an interruption in deposition, or b) by the erosion of depositionally continuous strata followed by renewed deposition.

Several types of unconformable boundaries are recognized:
  • nonconformity—an unconformity between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock
    .
  • angular unconformity—an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers
    .
  • disconformity—an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition.

  • conformable boundary—an arrangement where layers of sedimentary strata are parallel, but there is little apparent erosion and the boundary between two rock layer surfaces resemble a simple bedding plane.
Types of unconformities
Fig. 1-77. Types of unconformities (boundaries between layered rocks)
 
Grand Canyon Grand Canyon block diagram The Waterpocket fold in Capitol Reef National Park Utah Sedimentary layers at the Del Mar Dog Beach
Fig. 1-78. Rock formations exposed in the Grand Canyon were originally deposited in Precambrian and Paleozoic Eras. Some layers were deposited in shallow oceans, others on land. Fig. 1-79. A block diagram of the Grand Canyon shows the name of rock formations separated by unconformities (representing "gaps" in time). Can you spot an angular unconformity? Fig. 1-80. Rock formations like these in Utah record information about 100 million years of Mesozoic Era of the region. These sedimentary rock layers were originally deposited horizontally. Fig. 1-81. Layers of sedimentary rock formations of the Cenozoic Era are exposed in many locations along the California coastline. These are located at the Dog Beach in Del Mar, CA.
Chapter 1 quiz questions
http://geologycafe.com/oceans/chapter1.html 1/1/2016