Geography Test 3: Section 1

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geomorphology INTRO - Earth's Internal Structure

geomorphology

The science of landforms; their origin, evolution, form, and spatial distribution

landform

individual element of a landscape EX: a mountain, a river, a hill, etc.

topography

Earth's ridges, valley's & other surface features; the change in elevation over the Earth's surface

uniformitarianism

The theory that geologic events (and others) are caused by natural processes, many of which are operating at the present time

tectonic

developed by the rearrangement of the Earth's crust, driven by internal energy

fluvial

developed by moving liquid water

glacial

developed by glacial (frozen) water

coastal

developed by waves

eolian

developed by wind

steady-state equilibrium

little change, with inputs and outputs equal

dynamic equilibrium

fluctuates around an average value, but demonstrates a trend over time

geomorphic processes

relationship between external and internal processes and forces

internal processes

those processes which occur or originate within Earth's crust; volcanism, diastrophism (mountain building), plate tectonics (massive crustal rearrangements)

external processes

those processes which occur on the Earth's surface; weathering & erosion by fluvial, glacial, eolian, & coastal

P waves

push or compressional waves

S waves

shear or shake waves

L waves

surface waves, the ones we see

Earth's Internal Structure

Concentric layers, with heavier layers towards the center, each layer distinct in chemical composition and temperature

Seismic waves

3 Types: P, S, & L waves, evidence for differing levels b/c waves change with changes in the Tº and density of material, cooler = higher velocity, hotter = slower velocity

Inner Core

solid and rigid, made of Fe and Ni

Outer Core

liquid (molten), more plastic, made of Fe and Ni and lower pressure and lower T's

Gutenberg Discontinuity

an uneven, broad transition zone between the Outer Core and the Lower Mantle

Lower mantle

solid, oxides of Fe, magnesium (Mg), and silicon (Si)

Upper mantle

partially molten, consists of silicate minerals

Asthenosphere

molten, source of magma which pushes up into the crust & onto the surface

Lithosphere

Uppermost, solid portion of mantle, plus the crust, zone of contact btw the Uppermost mantel and the crust is the Mohorovicic,

Continental Crust

lower density, silica or sail rock, ex: granite, shale, or marble

Oceanic Crust

higher density, somatic bricks or sima, ex: basalt & lava

Craton

each continent has a core or nucleus of crystalline rock

Continental shield

an exposed craton

Mt. Everest, 29,035 ft

highest point above sea level

Mariana Trench, -36,198 ft

lowest point below sea level

Geologic Time Scale

a method of indicating the age of the Earth, a sequence based on relative positions of rock strata (layers), RELATIVE TIME SCALE

Geologic Cycle

The vast cycling of material that occurs in and on the lithosphere, encompassing the hydrologic, tectonic, & rock cycles; the building and wearing down of landforms

Hydrologic Cycle

movement of water

Tectonic Cycle

movement of crustal material and magma

Rock Cycle

formation of the three basic types of rocks

Mineral

an element or combination of elements that forms an inorganic natural compound which has specific qualities, such as a unique crystalline structure, hardness

Rock

an assemblage of minerals bound together, usually 2-5 different materials

Igneous Process & Rocks

formed by crystallization of magma; the solidifying of magma (lava) either below or on the surface

Intrusive Types

form below the surface within the crust (ex: plutons, batholiths, laccoliths); make up many mountain ranges with exposed plutons

Extrusive Types

forms on the surface of the crust (ex: lava or basalt, volcanic ash, obsidian, pumice); makes up ocean floor with primarily basaltic igneous rock

Sedimentary Process & Rock

formed from existing material by weathering, erosion, transport, and deposition

Lithification

the cementation, compaction and hardening of sediments into rock

Clastic Rock

made from bits & pieces of former rocks; these are visible pieces, such as the sand at the beach or the soil in your backyard (ex: sandstone, shale, siltstone, conglomerates)

Non-clastic/Chemical Rock

(sedimentary) made from minerals dissolved in solution (water); the material, such as various salts, dissolved in a river, lake or ocean (ex: limestone, coal, evaporites (salts), chalk, gypsum)

Metamorphic Process & Rock

formed from existing material by physical and/or chemical change under high pressure and/or high temperature

Contact Metamorphism

change brought about by magma touching ("cooking") the adjacent rock; usually more compact than original material & thus harder

Foliated Rocks

minerals within original rock are rearranged to form distinct bands or striations after metamorphism (ex: slate, schist, gneiss, mylonite)

Non-foliated rocks

more homogenous mixture and few or striations
(ex: quartzite, marble, greenstones)

Mohorovicic

zone of contact between the upper mantle and crust

Superposition

assumption that younger rocks and sediments are at the top of a formation and older materials are nearer to the bottom

Paleomagnetism

magnetic alignment of charged particles (esp. Iron material) in the rock which exhibit a symmetrical pattern as you move away from the mid-oceanic ridge.

Sea-floor spreading

the movement of crustal material by the upwelling of magma along a system of mid-oceanic ridge

Plate tectonics

combined the ideas of sea-floor spreading, continental drift, paleomagnetism and other ideas.; the theory covering crustal movements and the foundation of crustal tectonic processes

Convergent

where plate are moving/coming together, under compressional stress

Transform/Lateral

where plates are sliding past one another

Oceanic-continental

oceanic crust (which is denser) is subducted (forced) under the continental crust (which is less dense) & re-melted in the Asthenosphere

Oceanic-oceanic

subduction of one plate & re-melting of it

Continental-continental

areas of great compression & mountain building , high earthquake activity, but little or no volcanism, little or no subduction of continental crustal material

Theory of thermal convection

suggests that the continents were driven by huge convective cells within the asthenosphere

Extrusive volcanism

when magma (lava) flows out onto the Earth's surface and then cools to form igneous rock

Volcanism

The processes by which magma and gases are transferred from the Earth's interior to near or on the surface.

Volcano

a landform with a vent, or fissure(crack) on the surface which is the end of a conduit originating from below the crust in the Asthenosphere

Magma chamber

where magma is collected below the volcano before being expelled

Crater

the surface depression at the summit of the volcano

Lava

the term used for magma once it has erupted onto the Earth's surface

basaltic or mafic lava

high in Mg & Fe, < 50% silica thus less viscous which means it flows readily, and thus less gas is trapped within leading to a less explosive eruption

felsic lava

richer in silica thus more viscous meaning it flows slower: it is also more acidic, and more gases are trapped leading to more explosive eruptions

pyroclastics or tephra:

fragments expelled explosively from a volcano, quite common with felsic magma (explosive eruptions)

Effusive eruption

relatively gentle, non-violent eruptions because gases readily escape, thus less explosive; mostly mafic lava

Explosive eruption

relatively violent eruptions because conduit often gets plugged with cooled/solidified magma, and thus a greater amount of gases are trapped in the magma, increasing pressure

lahar

a flood of ash, mud, & water created by melting of snowcap during an eruption or volcanic event

pyroclatic flow

a cloud of hot volcanic gas & ash that moves down the flanks of the volcano

Phreatic eruptions

violent, explosive eruptions made more severe by water entering the magma chamber, increasing pressure from steam, & increasing the explosive power

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