GEOG 2300: CHAPTER 12
41 Cards in this Set
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Endogenic system
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-internal processes that produce flows of heat and material from deep below Earth's crust
-tectonics, earthquakes, volcanism
-radioactive decay is main energy source
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exogenic system
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-Earth's external surface system
-powered by insolation, which energizes air, water, and ice and sets them in motion, under the influence of gravity.
-river, landforms,weathering, erosion, oceans, glaciers
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The principle of uniformitarianism
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-"The present is the key to the past"
-The laws of nature have not changed in the course of time
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Principle of superposition
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Rock & sediment are always arranged with youngest bed “superposed” toward the top of a formation and the oldest at the base -- if they have not been disturbed.
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Stratigraphy
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scientific study of any layered (stratified) rock
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Relative time
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determines the sequence in which events occurred, without reference to actual time periods.
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absolute time
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actual date
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How old is the solar system?
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-4.6 byo
-a few rocks survive from earth's early days (4.4 byo)
-solar system formed around the same time
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Earth is how old?
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4.6 BYA
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How old is the Moon?
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4.5 billion years old (30 million less than Earth)
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radiometric dating
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-can determine absolute ages of fossils
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Half-life
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Amount of time it takes 1/2 of a radioactive isotope to disappear into daughter isotope
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geologic time scale
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eon-era-period-epoch (largest to smallest)
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Holocene
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-Of relating to the present geologic epoch (youngest)
-characteristic of post glacial conditions
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Anthropocene
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Age of Man, a new geologic epoch , impact of humans on earth's systesm
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Formation of Earth
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-thought to have condensed from a nebula of dust, gas and icy comets about 4.6 b.y.a
-silica and iron are tow dominant materials
-during early stages of formation, earth's temp was so high that silica and iron were in a liquid state
-as temp decreased, earth solidified and gravity sort…
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earth's core
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-inner (solid iron)
-outer (liquid shell composed primary of molten iron)
-core mass= 1/3 of earth's mass
-core volume= 1/6 of earth's volume
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Earth's Magnetism
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-The fluid outer core generates at least 90% of Earth's magnetic field
-migration of the north magnetic pole
-magenetic and geographic poles are different
-geomagnetic reversals (polarity has reversed)
-magnetic materials in rocks align according to position of magnetic pole
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Mantle
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-lower and upper
-consists of 80% of earth's total volume
-average depth 2900 km
-average density is 4.5g/cm3
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Moho
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the boundary between the crust and the uppermost mantle
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Asthenosphere
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-plastic like layer between the upper mantle and the uppermost mantle
-weak, ductile layer of mantle beneath the lithosphere that deforms to accommodate the horizontal and vertical motions of plate tectonics
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Lithosphere
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-consists of the crust and uppermost mantle
-strong, rocky outer shell of solid earth that forms tectonic plates
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seismic waves
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-used to probe earth's internal structure and density profile
-seismic waves travel at a higher speed in the cooler and more rigid areas than the hotter and softer areas
-plastic zones absorb seismic waves
-density changes could induce reflection and refraction of seismic waves
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Adjustments in the crust: buoyancy and isostasy
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-buoyancy tells us that something less dense floats in something denser
-earth's crust floats on the denser layers beneath
-where the load is greater, the crust tends to sink, or ride lower in the asthenosphere;without that load, the crust rides higher in a recovery uplift called isosta…
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Isostatic Adjsutment
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-isostatic refers to the state of gravitational equilibrium between the lithosphere and asthenosphere such that the tectonic plates float at an election that depends on their density
-as land loses mass, the crust isostatically adjusts upward
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mineral
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an inorganic (nonliving) natural compound having a specific chemical formula and possessing a crystalline structure
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rock
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-an assemblage of minerals bound together, or a mass of a single mineral, or undifferentiated material, or even solid organic material
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3 rock types
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-Igneous (fire formed, molten: intrusive and extrusive)
-sedimentary (from settling out)
-metamorphic (altered)
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Intrusive Igneous Rock
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Rock formed by the cooling of magma just under the surface of the Earth
ex. Granite
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Extrusive Igneous Rock
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Igneous rock that has formed on earths surface; cools quickly
ex: basalt
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Rock Cycle
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sedimentary undergoes heat, intense pressure (metamorphism)
metamorphic rock melts into magma, which then cools and solidifies (crystallization) turns into igneous rock
igneous rock weathers, erodes, deposition, transports, turing into sediments, which then compact, cementation, chemica…
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Sedimentary Processes
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1. As it reaches the surface, it encounters weathering and erosion and breaks down into sediment
2. Sediment is transported
3. Then it is deposited and becomes a very thick pile
4. Compaction and cementation
Sandstone, Limestone
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Metamorphic Rock
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-any type of rock can be transformed to metamorphic
-formed under intense heat and pressure
-found in ancient roots of mountains
-bottommost layers of sedimentary rock due to weight of overlying sediments
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Continental Drift
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Theory that proposed that the present continents were originally connected as one or two large landmasses that have broken up and literally drifted apart over the last several hundred million years.
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Pangaea
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supercontinent of all continents
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Plate tectonics
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lithosphere is divided into a number of plates that float independently over the mantle and along whose boundaries occur the formation of new crust, the building of mountains, and the seismic activity that causes earthquakes
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Sea floor spreading
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-The process of forming new ocean crust
-newest oceanic crust along ridges, older further away
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convergent plate boudnary
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-plates moving toward each other
-continent-oceanic
-continent-continent
-oceanic/oceeanic
-marked by deep ocean trenches and volcanic arcs; experience volcanic activity and mountains
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Divergent Plate Boundary
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-were plates move apart and new oceanic crust is formed
-stretch and separate; create lithosphere along mid ocean ridge
-causing volcanic eruptions and earthquakes
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transform plate boundary
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-Two plates sliding past each other in opposite directions
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evidence for testing plate tectonics
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-seafloor spreading
-magnetic reversal
-age of sea floor
-earthquake and volcanic activity
-hot spots
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GEOG 2300: CHAPTER 12