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)

Fall

Mass Wasting- rock moves through air from gravity (leaves talus deposit at bottom)

Slide 

Mass Wasting- in mountains rock and soil is detached but stay in contact with slope

Slump

Mass Wasting- type of slide where rock moves downward while rotating backward

Flow

Mass Wasting- unstable bc of added water. There is earthflow and mudflow

Creep

Mass Wasting- slowest gradual downhill movement of the regolith