GEOL 110 LEC Exam 2 (Baedke - JMU)

Elastic Deformation

Nonpermanent, rock returns to original shape (small mounts of stress)

Ductile Deformation

Permanent, rock flows or bends (mid-level stress - occurs in folds)

Brittle Deformation

Permanent, rock breaks (high amounts of stress - occurs in faults)

Compressional Forces

Squeezes and shortens the body of a rock

Tensional Forces

Stretches and tends to pull the body of a rock apart

Shearing Forces

Pushes two sides in opposite directions

Reverse Fault (Compression)

Head/hanging wall moves up relative to foot wall

Normal Fault (Tension)

Head/hanging wall moves down relative to foot wall

Right-Lateral Strike-Slip Fault (Shearing)

Offset to the right

Left-Lateral Strike-Slip Fault (Shearing)

Offset to the left

Strike-Slip Fault (Shearing)

No head/hanging wall or foot wall present - they just slide past each other

Anticline

Upwards crest, shaped like an "A", has oldest rocks in the middle, dips away

Syncline

Downward trough, shaped like the bottom of an "S", has the youngest rocks in the middle, dips toward

Monocline

Flat, horizontal folds (very rare)

Wilson Cycle

The opening and closing of ocean basins due to tensional forces pulling continents apart

Elastic Rebound Theory

Theory that a rock can withstand a certain amount of stress before it breaks and then builds that stress back up again (causes earthquakes)

Focus (Earthquake)

Where the earthquake begins inside the Earth; seismic waves originate here

Epicenter (Earthquake)

Point directly above the focus of the earthquake; located on the Earth's surface

Slip

The amount of movement an earthquake causes

P-waves (Primary Waves)

Body waves, travel fast and in one direction, compressional, move through any material, first to be felt

S-waves (Secondary/Shear Waves)

Body waves, travel slow and in more than one direction, move through solid material only

Surface Waves

Seismic waves that travel along the surface of the Earth, NOT through

Richter Scale

Logarithmic scale used for Earthquake magnitude from 1-10 that is 10x the intensity and 30x the energy from one number to the next

Tsunami

Waves generated by the lifting of the ocean floor

How does density relate to the speed of seismic waves?

The more dense the material, the faster the seismic waves move

What waves are constantly bent as they move through the Earth?

P-waves and S-waves (body waves)

Oceanic Crust

Thinner, more dense, darker in color, mafic, Basaltic

Continental Crust

Thicker, less dense, lighter in color, felsic, Granitic

Isostasy

Continental crust floats on top of oceanic crust

Moho

P-waves below travel faster than P-waves above

Mantle

Low velocity zone; P-waves and S-waves decrease

Asthenosphere

Mafic materials; low velocity zone so seismic waves pass slower

Inner Core

Solid, fast moving waves, very dense

Outer Core

Liquid

What has the North Pole done many times?

Flipped

Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian

Carl's Old Shirt Doesn't Match Pete's Pants

Original Horizontality

Flatlying rocks are deposited and then tilted

Superposition

Rocks are superimposed on top of each other; youngest at the top, oldest at the bottom

Cross-Cutting Relations

A dike cuts across all of the other rocks; the dike is younger than all of the other rocks

Relative Age Dating

Age of sedimentary rock layers in relation to one another

Absolute Age Dating

Number of years since the rock formed

Nonconformities

Sedimentary rocks lie on top of igneous rocks

Disconformities

Erosion removes a part of otherwise undisturbed rock

Angular Unconformities

Rocks below are at an angle in relation to those above

Half-Life

Amount of time it takes for half of the radioactive parent material to decay into the nonradioactive daughter product

What supports the theory of continental drift?

Continental fit (supercontinent Pangea), rock sequences, glacial evidence, fossil evidence, and polar wandering (continents wander, NOT poles)

What supports the theory of plate tectonics?

Seafloor spreading and age dating of rocks

1972

Old idea of continental drift was abandoned and new idea of plate tectonics was accepted by the geologic community

OC-OC (Ocean Crust-Ocean Crust)

Subducted plate melts and that material erupts at volcanic arcs

OC-CC (Ocean Crust-Continental Crust)

Plates collide and OC is subducted underneath CC; subducted plate melts and that material rises and erupts at volcanoes

CC-CC (Continental Crust-Continental Crust)

Compressional forces cause faulting and thickening of crust