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World
Geography Outline of Lecture
1. The Universe Big Bang Theory Hubble Singularity Expanding Universe Background Radiation Age: 13.7 billion years old 2. The Theory of Everything Forces in Nature Newton’s Theory of Gravity Maxwell’s Theories of Electro-Magnetism Einstein’s Theory of Relativity Quantum Mechanics String Theories. Multiverse Parallel Universes 3. Evolution of Galaxies and Stars 4. Our Solar System Hellenistic Science Ptolemaic System—Geocentric Modern Science Copernican System—Heliocentric The Nebula Hypothesis of our Solar System The Inner Planets Mercury, Venus, Earth, Mars The Outer Planets Jupiter, Saturn, Uranus, Neptune Asteroid Belt Pluto 5. The Earth Crust Lithosphere Asthenosphere Mantle Core 6. Lithosphere 12 large and many smaller plates Plate Tectonics Subduction 7. Geologic Time Earth is 4.6 billion years old Geologic Time Periods Continental Drift Alfred Wegener Pangea—225 million years ago Ice Ages Age of Mammals—64 million years ago Evolution of Humans—7 to 6 million years ago 8. The Rock Cycle Igneous Rocks Sedimentary Rocks Metamorphic Rocks 9. Formation of Landforms Tectonic Forces Diastrophism Broad Warping Folding Faulting Earthquakes Tsunamies Volcanism Gradational Processes Weathering Mechanical Weathering Chemical Weathering Mass Movement Avalanche Landslide Erosional Agents and Deposition Running Water Waves and currents Wind 10. Landforms Landform Regions based on the height above seal level of the terrain. Lowland Terrain Flatlands: plains with local relief less than 100 feet Rolling Plains: local relief between 100 and 300 feet Hilly Plains: Level terrain with occasional hills and mountains: local relief less than 3000 feet Highland Terrain Plateaus and Tablelands: level areas elevated above general terrain Hills: Local relief less than 3000 feet. Mountains: Local relief greater than 3000 feet Ice Caps
Formation
of the Earth The solar system formed about 4.6 billion years ago.
The Nebular Hypothesis is the most plausible explanation for its origins.
For a complete WEB course on our solar system check out this site:
http://csep10.phys.utk.edu/astr161/lect/index.html The
Nebular Hypothesis http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html “The Nebular
Hypothesis in its original form was proposed by Kant and Laplace in the 18th
century. “A great cloud of gas
and dust (called a nebula) begins to collapse because the
gravitational forces that would like to collapse it overcome the forces
associated with gas pressure that would like to expand it (the initial collapse
might be triggered by a variety of perturbations---a supernova blast wave,
density waves in spiral galaxies, etc.). “It is unlikely that
such a nebula would be created with no angular momentum, so it is probably
initially spinning slowly. Because of conservation of angular momentum, the
cloud spins faster as it contracts. “Because of the
competing forces associated with gravity, gas pressure, and rotation, the
contracting nebula begins to flatten into a spinning pancake shape with a bulge
at the center. “As the nebula collapses
further, instabilities in the collapsing, rotating cloud cause local regions to
begin to contract gravitationally. These local regions of condensation will
become the Sun and the planets, as well as their moons and other debris in the
Solar System. “While they are still
condensing, the incipient Sun and planets are called the protosun and protoplanets,
respectively.” Geologic
Time Geologic Time. The
earth is old and geologic time is
measured in billions of years. The
earth is about 4.6 billion years old. Geologic time is divided
into eons, eras, epochs, and periods. There
are two eons: Phanerozoic Eon and
the Precambrian Time or Eon. See
page below. Inside
the Earth http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html). The earth is divided into
several layers: Inner Core, Outer
Core, Mantle, and Crust. Crust. The crust,
the outermost layer, is rigid and very thin compared with the other two. Beneath
the oceans, the crust varies little in thickness, generally extending only to
about 5 km. The thickness of the crust beneath continents is much more variable
but averages about 30 km; under large mountain ranges, such as the Alps or the
Sierra Nevada, however, the base of the crust can be as deep as 100 km. Mantle: Below the crust is
the mantle, a dense, hot layer of semi-solid rock approximately 2,900 km
thick. The mantle, which contains more iron, magnesium, and calcium than the
crust, is hotter and denser because temperature and pressure inside the Earth
increase with depth. Core. The
Earth's core is actually made up of two distinct parts: a 2,200 km-thick liquid
outer core and a 1,250 km-thick solid inner core. As the Earth rotates,
the liquid outer core spins, creating the Earth's magnetic field. Outer Core:
2900 km down; 2200 km thick; Mostly
Liquid Iron and about 10% molten Sulpher (Fe, S): 2800 degrees Celsius Inner Core: 5200 km down; 1250 km thick; Solid Iron (Fe); 4300 degrees Celsius Plate Tectonics The upper mantle and crust
are made up of two distinct layers called the Asthenosphere and
the Lithosphere. Lithosphere is made up of
the crust and the top layer of the mantle.
It is solid. “The
lithosphere is broken into about 12 large and many small rigid plates, each of
which, according to the theory of plate tectonics, slides or drifts very slowly
over the heavy semi-molten asthenosphere. A
single plate often contains both oceanic and continental crust.” (Getis, 61) The part of the mantle
near the crust, about 50-100 km down, is especially soft and plastic, and is
called the asthenosphere. The top part of the mantle and the crust make up the
lithosphere Asthenosphere.
Below the lithosphere is a layer of the mantle called the Asthenosphere.
This layer is soft and plastic, like slush. The tectonic plates of the
lithosphere float on the asthenosphere. “The mantle and crust
above are cool enough to be tough and elastic, and are known as the lithosphere.
A heavy load on the crust, like an ice cap, large glacial lake, or
mountain range, can bend the lithosphere down into the asthenosphere, which can
flow out of the way. The load will sink until it is supported by buoyancy.
If an ice cap melts or lake dries up due to climatic changes, or a mountain
range erodes away, the lithosphere will buoyantly rise back up over thousands of
years. This is the process of isostatic rebound.” (http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html) Convection in the Earth’s Mantle. http://earth.leeds.ac.uk/~greg/Conv.html See Pangaea and Tectonic Plates pages below. Geomorphology Geomorphology is a branch of the fields of geology and physical geography. It “is the study of the origin, characteristics, and development of landforms. It emphasized the study of the various processes that create landscapes. Geomorphologists examine the erosion, transportation, and deposition of materials, and the interrelationships among climate, soils, plant and animal life, and landforms.” (Getis, 58). Landforms Landforms. “Two
types of forces interact to produce those infinite local variations in the
surface of earth called landforms: (1)
forces that push, move, and raise the earth’s surface; and (2) forces that
scour, wash, and wear down the surface. Mountains
rise and are then worn away. The
eroded materials—soil, sand, pebbles, and rocks—are transported to new
locations and help to create new landforms.” (Getis, 58) Rocks Rocks. Rocks
can be classified by their chemical composition and their physical
characteristics. But, they can also be classified by the way in which they
were formed. The three main forms
of rocks are: igneous, sedimentary,
and metamorphic. Igneous Rocks. “Igneous
rocks are formed by the cooling and solidification of molten rock. . . . The
name for underground molten rock is magma;
above ground it is lava. Intrusive
igneous rocks are formed below ground level by
the solidification of magma, whereas extrusive igneous rocks are
created above ground level by the solidification of lava.” (Getis, 58) “The composition of
magma and lava and, to a limited extent the rate of cooling determine the
minerals that form. The rate of
cooling is mainly responsible for the size of the crystals. Large crystals of quartz, a hard, dense mineral, form slowly
beneath the surface of the earth, where cool air is not available.
When combined with other minerals, quartz forms the intrusive igneous
rock called granite. “The
lava that oozes out of the earth’s surface and makes up a large part of the
ocean basins become the extrusive igneous rock called basalt,
the most common rock of the earth’s surface.
If, instead of oozing, the lava erupts from a volcano crater, it may cool
very rapidly. Some of the igneous
rocks formed in this manner contain cavities and are light, such as pumice.
Some may be dense, even glassy, as is obsidian.
The glassiness occurs when lava meets standing water and cools
suddenly.” Getis, 58-9) Sedimentary Rocks. “Sedimentary rocks evolve under water in horizontal beds called strata. Usually one type of sediment collects in a given area. If the particles are large and rounded—for instance the size and shape of gravel—a gravelly rock called conglomerate forms. Sand particles are the ingredient for sandstone, while silt and clay form shale or siltstone. “Sedimentary
rocks also derive from organic material, such as coral, shells, and marine
skeletons. These materials settle into beds in shallow seas, forming limestone.
If the organic material forms mainly from decomposing vegetation, it can
develop into a sedimentary rock called bituminous coal. Petroleum is also a
biological product, formed during the millions of years of burial by chemical
reactions that transform some of the organic material into liquid and gaseous
compounds. The oil and gas are
light; therefore, they rise through the pores of the surrounding rock to places
where dense rocks block their upward movement. “Large
parts of the continents contain sedimentary rocks. For example, nearly the entire eastern half of the United
States is overlain with these rocks. Such
formations indicate that in the geologic past, seas covered even larger
proportions of the earth than they do today.” (Getis, 59 – 60)
Why did the seas cover larger areas of earth? Metamorphic Rocks. “Metamorphic
rocks are formed from igneous and sedimentary rocks by earth forces that
generate heat, pressure, or chemical reaction.
The word metamorphic means
“changed shape.” The internal earth forces may be so great that heat and
pressure change the mineral structure of a rock, forming new rocks.
“For example, under great pressure, shale, a sedimentary rock, becomes slate, a rock with different properties. Limestone, under certain conditions, may become marble, and granite may become gneiss (pronounced nice). Materials metamorphosed at great depths and exposed only after overlying surfaces have been slowly eroded away are among the oldest rocks known on earth. Like igneous and sedimentary rocks, however, their formation is a continuing process.” Getis, 60) Rock
Cycle The Rock Cycle. “All
rocks are part of the rock cycle through
which old rocks are continually transformed into new ones by” two processes.
“No rocks have been preserved unaltered throughout the earth’s
history.” “Two principal processes
alter rocks (1) the forces that tend to build landforms up; and (2) the
gradational processes that wear landforms down.” “Rocks are the constituent ingredients of most landforms. The strength or weakness, permeability, and mineral content control the way rocks respond to the forces that shape and reshape them” and thus this planet. (Getis, 60) Forces Shaping Our Planet Tectonic
Forces The earth’s crust is
altered by the constant forces resulting from plate movement.
Tectonic (generated from within the earth) forces are of two types, either
diastrophic or volcanic. Diastrophism
is the great pressures acting on the plates
that deforms them by folding twisting, warping breaking, or compressing rock. Volcanism
is the force that transports heated
material to or toward the surface of the earth. Diastrophism Broad
Warping Folding Faulting Volcanism Gradational
Processes Weathering
Mechanical Weathering
Chemical Weathering Mass
Movement Erosional
Agents and Deposition
Running Water
Stream Landscapes
Stream Landscapes in Humid Areas
Stream Landscapes in Arid Areas
Groundwater
Glaciers
Waves, Currents, and Coastal Landforms
Wind Landform Regions “A
large section of the earth’s surface where a great deal of homogeneity occurs
among the types of landforms that characterize it.” (Getis, 85) Mountain
belts Plains Plateau _______________ U.S. Geological Survey Newman, William L. Geologic Time (U.S. Geological Survey, 1997) Available online http://pubs.usgs.gov/gip/geotime/contents.html |