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Physical geography study guide answers ch. 12 to ch. 19

continental drift theory

wegener 1912. Land masses were once united(pangaea). Split into laurasia(north) and gondwandaland(south). further broke into smaller units + moved in continental drift. Atlantic ocean = 150mill yrs old

What kind evidence support the tectonic theory

Shapes, glacial scarring marks, rare fossils, sedimentary rocks. failed to explain earths crust is to rigid to permit motions + energy needed to move.

What types of boundaries exist between plates ?

divergence(seafloor spreading). convergence(collision). latteral(transform)

spreading center

a linear zone in the sea floor along which magma rises and from which adjacent crustal plates are moving apart. The region at the crest of a mid-ocean ridge, where new crust is being formed by seafloor spreading.

How plate tectonic theory explain the global distribution of earthquakes ?

occur when tectonic forces cause rock to suddenly fracture and move, shaking the ground in the vicinity of the fracture

Types of faults

Normal fault(occurs when lithospheric plates move apart/part drops down),thrust fault(plates move together then pressure pushes 1 up), strike-slip(move horizontal +push apart), Overthrust fault(combo of horizontal passing + vert. pushing)

Volcanoes distribution, types of volcanoes?

Many volcanoes are located along the subduction boundary, others located on or near spreading centers

spreading boundary

spreading boundary(where plates move apart) - New lithosphere is being formed by accretion. EX. Seafloor spreading along the axial rift

converging boundary

(plates collide) - Subduction is in progress, and lithosphere is being consumed. EX. Active continental margin

transform boundaries

plates move past one another on a transform fault. EX. transform boundary associated with mioceanic ridge.

Normal fault

(occurs when lithospheric plates move apart)an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall

transcurrent fault

(occurs when 2 rock masses move horizontally past each other), a horizontal movement fault so there's no hanging wall or footwall. san andreas fault in california is a famous one.

Reverse fault

a geological fault in which the upper side appears to have been pushed upward by compression, earths crust is shortened

Overthrust fault

one block rides up on top of the other along a near-horizontal fault plane; Akin to a low-angle reverse fault; Crust 'snaps' after severe folding; assoc. with orogeny


form from the eruption of thick, gassy, felsic lavas and are most common along the converging plate boundaries of the Pacific rim. They have steep sides and often produce explosive eruptions that form calderas. Stratovolcanoes may also emit a glowing cloud of white-hot gases and fine ash that travels very rapidly (pyroclastic flow), searing everything in its path.

shield volcanoes

Broadly rounded shield volcanoes form over hotspots and along midoceanic ridges where more fluid, less gassy mafic (basaltic) lavas erupt. These lavas can form vast flood basalts when they erupt on continents.

Physical weathering

the disintegration of rock into smaller fragments of the same mineral composition by processes such as freezing, exfoliation, biological action.

Chemical weathering

weakening of the rock by slow chemical reactions: hydrolysis(chemical union of water with another substance to produce a new compound), oxidation(chemical reactions of oxygen w/ minerals), carbonation(carbon dioxide combines with water forming carbonic acid: H2O + CO2 = H2CO3 carbonic acid reacts w/ the calcium carbonate to form calcium bicarbonate which is carried away in solution.

Mass wasting

the downslope movement of rock and or soil by gravity

slow movements(mass wasting)

Soil Creep: very slow, result of freezing + thawing Solifluction: Happens in permafrost landscapes(year round frozen ground)water saturates above permafrost and flows down hills. Earth Flows: a portion of slope flows downhill. Slow limited extent

freezing-thaw action(Frost action)

one of the most important physical weathering processes in cold climates. When water freezes in joints in the rock, the expansion of the water during repeated freezing cycles forces the joints to enlarge.


a form of physical weathering that occurs when overlying rock layers are removed through erosion. This causes the rock to expand and crack in layers parallel and vertical to the surface.

Salt crystal weathering

operates extensively in dry climates and is the result of the growth of salt crystals in rock pores. Groundwater moves to the surface through capillary action and evaporates, leaving the salts behind producing grain by grain breakup of sandstone.

physical weathering (heat/plants)

Physical weathering can also occur when rocks are subject to intense heating and cooling and through the growth of plant roots that can wedge rocks apart.

Soil creep

very slow, result of freezing(expands)/thawing(contracts)


happens in permafrost landscapes(year round frozen ground layers). Water saturates above the permafrost and flows downhill

earth flow

a portion of slope flows downhill. Slow/limited extent.


piles of rocks at the bottom of slops

water budgets (examples)

Evapotranspiration, Overland flow, Infiltration, Baseflow, Runoff, Subsea outflow, Precipitation

saline lakes

lakes with no surface outlet, can form beneath sea level Ex. Caspian Sea and Dead Sea. When dried up create salt beds.

Ground water and karst landforms

Ground water refers to water beneath the Earth's surface that fully saturates the pore spaces in bedrock, regolith, or soil. The movement of ground water through highly soluble limestone rock produces a distinctive landscape referred to as a karst landscape.

precipitation paths

The soil layer plays an important role in determining whether precipitation will be directed to the atmosphere by evapotranspiration, to groundwater by percolation, or to streams and rivers as overland flow.

unstaturation zone, saturated zone, water table

The water table marks the upper surface of the saturated zone where the pore spaces in rock and regolith are completely filled or saturated with water. the unsaturated zone is above.

karst landforms

limestone area where sinkholes are numerous and small surface streams are non-existant. The movement of ground water through highly soluble limestone rock produces a distinctive landscape referred to as a karst landscape.


Surface depression in limestone, leading down into limestone caverns. A hole formed when limestone is dissolved, causing the land above to collapse


steep mounds or spikes of calcium carbonate that grow up from the floor of a cave


thick, icicle-shaped formations that grow down from the ceiling of a cave


limestone caverns are interconnected subterranean cavities in bedrock formed by the corrosive action of circulating ground water on limestone

Drainage basin

consists of a branched network of stream channels and adjacent slopes that feed the channels. It is bounded by a drainage divide.

drainage divide

is the line of seperation(ridge) between runoff that descends in the direction of the drainage basin in question and runoff that goes toward an adjacent basin

stream order

energy and nutrient flow that increases as water moves toward the ocean (e.g.,the smallest stream (primary) that ends when rivers flow into oceans)


the chemical union of water with another substance to produce a new compound


carbon dioxide combines with water forming carbonic acid. Carbonic acid reacts with the calcium carbonate to form calcium bicarbonate, which is carried away in solution.

cinder cone volcano

miles span and 1000ft vertical. fairly steep slopes+ crater at the top

strato volcano

smaller mt. base. steep slope(30 deg). ex. mount st. helens

shield volcano

has broad/GENTLE slopes. built by the eruption of fluid basalt lava. the widest volcanoes on earth. EX. maui

Rapid Movement(mass wasting)

Mudflow/Debris Flow: movements in drainage channels. fast.

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