Physical Geography Exam 4

Alfred Wegner- his theory, his evidence, and why it was rejected

Continental drift, because of coastlines and glacial deposits fitting together, no mechanism for how the plates moved

3 pieces of evidence for plate tectonics

Midocean Ridges, Paleomagnetism (Earth’s magnetic field reversals), and Seafloor Spreading

Divergent Plate Boundaries

Move apart, magma fills the gap; Mid-Atlantic Ridge and East Pacific Rise

Convergent Plate Boundaries (3 kinds)

Move together

Ocean-Continent- ocean is forced down

Ocean-Ocean- bigger piece forced down

Continent-Continent-pushes upward 

Transform Plate Boundaries

two plates slide past each other, causes earthquakes

Pacific Ring of Fire; location and what occurs here

Along fault lines, West side of the Americas and East side of Asia. Volcanos, earthquakes, and mountains are prevalent.

Hot Spots

Plate interiors, above mantle plumes. Flood basalts (big outpouring of lava) and volcanos are made.

Accreted terranes

pieces of lithosphere that have collided and fused with other plates. Ex: Alaska and West Canada accreted to North America

Where do volcanos occur

Plate boundaries and hot spots

Felsic Magmas

High in silica, thick, clogs volcanic neck, explosive and violent (granite)

Mafic Magmas 

Low in silica, thinner, flows long distance, less explosive (basalt)

5 Volcanic hazards

Volcanic gases, lava flow, eruption column & ash fall, pyroclastic flow, volcanic mudflows

Describe each type of volcanic peak

Shield- broad and short, composite- steep and symmetrical, lava dome- small and irregular shape, cinder cone- small and conical, calderas- basin where volcano exploded or collapsed

Plutons

large bodies of magma that harden underground, revealed later by erosion

5 intrusive igneous features

Batholiths (largest), Volcanic Necks (“pipe” inside part of volcano), Laccoliths (bulge that pushes the Earth up), Sills (horizontal between Earth’s layers), Dikes (vertical sheets that form a ridge)

What is folding

Colliding, compressing boundary; sedimentary rock layers are warped (Appalachian Mountains)

Faulting 

Rock structures are displaced vertically or horizontally (Sierra Nevadas)

Horst 

block pushed upward by faulting 

Graben

block pushed downward by faulting

Denudation

processes that wear down the landscape; include weathering, mass wasting, and erosion

Weathering

breaking down of rock into smaller pieces “in situ” (in place)

Mass Wasting

short-distance downslope movement of rocks from gravity

Joints

cracks in rock, give nature more access to break rock down

4 types of mechanical weathering

Frost wedging (freezing/thawing of water), salt wedging (salt crystals building up and growing), temperature changes (rock itself expands and contracts), exfoliation (curved layers peel off in sheets like an onion)

4 types of chemical weathering

Oxidization (oxygen dissolved in water, rusting), hydration (water added to the compound), hydrolysis (water breaks up a compound), carbonation (CO2 dissolved in water, often reacts with limestone)

5 types of mass wasting

Fall (falls through air), slide (stays in contact with slope), slump (rock rotates backward while moving downward, flow (has added water), creep (very gradual downhill movement of regolith)

Most important agent of landscape modification

running water

Talus

pieces of rock that have fallen from a landform, forming a talus slope at the bottom

Interfluve

higher land that separates adjoining valleys 

Streamflow & Overland flow 

Streamflow- channeled movement of water 

Overland flow- water runs in sheet after rain

Drainage basin/watershed

area that contributes overland flow, streamflow, and groundwater to a stream

4 ways streams move solid material (based on particle size)

Solution (dissolved), Suspension (stream flow), Saltation (bouncing), Traction (rolling)

Alluvium

deposit of clay, silt, sand, and gravel left by flowing water in a valley

Stream competence

largest particle size carried

Stream capacity

maximum solid load transported

Difference between perennial and intermittent streams

Perennial has a permanent flow (are in humid regions) and intermittent have seasonal flow

Consequent and subsequent streams

consequent- follow initial slope

subsequent- flow along faults in right angels to connect to consequent

Dendritic stream drainage pattern shape

looks like a tree

How is streamflow measured

streamgages log water height and flow velocity

Flood recurrence interval 

probability of a particular size flood occurring 

Antecedent & superimposed streams

antecedent- was there first, before uplift occurred

superimposed- landscape started higher then eroded away

Knickpoint migration

waterfall edge is eroded, breaks off, and new knickpoint is made further back

Cutoff meader (oxbow)

part of river meander that is cut off, forming a lake, that will disappear

Natural levee

raised edges of river from deposition during flood stage

2 ways human attempt flood control on Mississippi River

dams & natural levees

Stream rejuvenation & 2 forms of it

Streams becoming more erosive from uplift of land under them. 

• Stream terraces- new valley floor

• Entrenched meanders- meandering stream incises into land making deep gorges 

What makes desert a specialized environment

Sand, impermeable surfaces, wind action, and ephemeral streams

Basins of internal drainage in the desert

Where water collects because it can’t get out to the oceans

Exotic streams and two examples

Permanent streams in desert that originate elsewhere that is wetter. Nile and Colorado River

Ephemeral streams

streams that are only briefly filled when it rains

Playa

dry lakebed in the desert

Saline lakes

permanent lakes in the desert that are high in salt

Aeolian erosion and two types

Erosion by wind. Deflation (loose material being blown away) and Abrasion (pitting by blowing sand against something)

3 types of Aeolian transportation

Suspension, saltation (bouncing), Traction (pushing & rolling)

Erg

sea of sand (type of desert landscape)

Reg

stony desert (type of desert landscape)

Desert varnish

Mineral coating from evaporation that holds rocks together in a sheet

Inselberg

Isolated hill in the desert that rises abruptly from a plain

Basin-and-Range formation

Have mountains and valleys, smoother lines. Alluvial fans are made at base of mountains

Mesa-and-Scarp formation

Flat topped surface with the sharp & steep cliffs

How much of Earth’s land was covered in ice in Pleistocene glaciation and how much now?

30% then and 10% now

Two types of glaciers

Mountain glaciers and Continental Ice Sheets (there are only two of these left, one in Greenland and Antarctica)

What is plucking, abrasion, and meltwater

plucking- picking up rocks and carrying them along

abrasion- bedrock is worn down from being ground with rocks embedded in glacier

meltwater- streams below glacier transport rocks and smooth bedrock below

Glacial flour and glacial milk

Flour is finely ground rock carried by a glacier & milk is suspended rock in meltwater

How long did the Ice Age last?

We’ve been in it for the past 2 and a half million years of Earth’s history, with many periods of ice accumulation and retreat. So not steady. Currently are in an interglacial period

Accumulation and ablation and what a zone of each is

Accumulation is addition of ice from snow and ablation is subtraction of ice from melting. The upper portion (accumulation zone) is where new ice exceeds amount lost. The lower portion (ablation zone) is where amount lost is more than new ice added here.

How did continental ice sheets develop and flow

Had original places of ice accumulation in subpolar regions and flowed outward from there.

Rouche Moutonnee

Rounded glacially eroded hill

Till

Rock debris deposited by glaciers

3 types of deposition by ice sheets

Moraines- Landform longer than it is wide, made of till. Marks glacier edges at different points

Kettles- Little depression from where a ice block, now melted, once was

Drumlins- low elongated hill much smaller than moraines and parallel to direction of ice movement

4 Glaciofluvial (meltwater) features

Outwash Plains- flat expanse with braided patterns of channels across it

Eskers- ridges left by stream tunnels

Kames- small steep mounds

Lakes- water filled in spaces created by the glacier

4 things created by erosion from mountain glaciers

Cirques- hollowed out basin, where the glacier originated

Aretes- serrated ridge that separates cirques

Horns- steep pyramid mountain peak where three cirques intersect

U-Shaped Valleys- eroded V shape into a U

Lateral, recessional, and terminal moraines

Lateral- buildup of till on sides of glacier

Recessional- show where ice front was stabilized for a while and then receded again

Terminal- ridge of till that shows maximum advance of glacier

What theoretically caused Pleistocene Glaciation

slight variations in solar outputs, the tilt of Earth’s axis, and amount of greenhouse gases in the atmosphere