Geological Deformation and Earthquakes

Practice flashcards covering key concepts related to geological deformation, faulting, and earthquake mechanics.

What is deformation in geology?

Deformation changes the character of rocks through displacement, distortion, or stress.

What happens to undeformed rocks?

Undeformed rocks have horizontal beds, spherical grains, and no folds or faults.

How are deformed rocks characterized?

Deformed rocks have tilted beds, metamorphic alteration, folding, and faulting.

What is displacement in terms of rock deformation?

Displacement is the change in rock location or spatial orientation.

What is distortion in rock deformation?

Distortion is a change in rock shape, which can include strain, stretching, shortening, or shearing.

Define stress in the context of geology.

Stress is the force exerted per unit area.

What is strain?

Strain is the physical change due to stress and is the result of deformation.

Explain compression in geological terms.

Compression squeezes material, shortens and thickens the crust, and drives collision and mountain building.

What is tension in geology?

Tension pulls material apart and drives continental rifting.

What is shear in the context of rock deformation?

Shear occurs when surfaces slide past one another; it doesn't thicken or shorten the crust.

What is brittle deformation?

Brittle deformation occurs when rocks fracture due to stress exceeding their strength.

What characterizes ductile deformation?

In ductile deformation, rocks flow or fold without breaking, exhibiting plastic behavior.

What are the typical depths for brittle and ductile deformation?

Brittle deformation occurs in the shallow crust, while ductile deformation occurs in deeper crust under higher temperature and pressure.

How does temperature affect deformation?

Warm conditions lead to plastic deformation, while cold conditions lead to brittle deformation.

What is the effect of pressure on rock deformation?

High pressure tends to make rocks deform plastically, whereas low pressure makes them fracture (brittle).

How does the rate of deformation affect rock behavior?

Fast deformation leads to brittle behavior, while slow deformation leads to plastic behavior.

How does rock composition affect its deformation?

Soft rocks typically deform plastically, while hard rocks exhibit brittle behavior.

What is strike in geological terms?

Strike is the line formed by the intersection of a horizontal plane with a tilted surface.

What does dip refer to in geology?

Dip is the angle of a tilted surface down from the horizontal.

What is the dip direction?

The dip direction is perpendicular to the strike.

Define joint in the context of geology.

A joint is a planar fracture without offset.

What is a vein in geological terms?

A vein is a fracture filled with minerals like quartz or calcite.

What distinguishes a fault from a joint?

A fault is a fracture with displacement, while a joint has no offset.

What is a normal fault?

In a normal fault, the hanging wall moves down, occurring under tension.

Describe a reverse fault.

A reverse fault occurs when the hanging wall moves up and takes place under compression.

What characterizes a thrust fault?

A thrust fault is a low-angle reverse fault with a dip of less than 30 degrees.

Define strike-slip fault.

In a strike-slip fault, blocks move horizontally, parallel to the strike.

What is a left-lateral fault?

In a left-lateral fault, the opposite block moves to the observer’s left.

What is a right-lateral fault?

In a right-lateral fault, the opposite block moves to the observer’s right.

What is fault breccia?

Fault breccia is shattered and crushed rock resulting from brittle faulting.

What is fault gouge?

Fault gouge is pulverized, powdered rock produced from fault motion.

What are slickenslides?

Slickenslides are grooves or lineations on fault surfaces that indicate the direction of slip.

What is a fault scarp?

A fault scarp is the surface exposure of a fault trace.

Define the fold hinge in geology.

The fold hinge is the line of greatest curvature in a fold.

What are fold limbs?

Fold limbs are the less curved sides of a fold.

What connects the hinges of successive layers in a fold?

The axial plane connects the hinges of successive layers.

What is a syncline?

A syncline is a fold that opens upward and has a trough shape.

Define anticline.

An anticline is a fold that opens downward, taking an arch shape.

Describe a dome in geological terms.

A dome is a fold with layers that dip away from the center.

What is a basin in geology?

A basin is a fold with layers that dip toward the center.

What characterizes a flexural-slip fold?

In a flexural-slip fold, layers bend and slip over one another.

Explain passive-flow fold.

In a passive-flow fold, hot, ductile rocks deform by flowing without breaking.

What is a monocline?

A monocline is a step-like fold caused by movement over a fault.

Define tectonic foliation.

Tectonic foliation is the parallel alignment of minerals formed by compression.

What is orogenesis?

Orogenesis is the mountain building process caused by compressional tectonics.

What types of rocks are formed during orogenesis?

Rocks formed during orogenesis include igneous and regional metamorphic rocks.

What is the tectonic setting of orogenesis?

Orogenesis typically occurs at convergent plate boundaries, especially in continent-continent collisions.

What is continental rifting?

Continental rifting involves normal faulting that creates fault-block mountains and basins.

What is decompression melting?

Decompression melting occurs due to thinning crust in rifting areas and can form volcanoes.

Explain delamination in the context of geology.

Delamination is the removal of deep lithosphere, leading to uplift.

What is orogenic collapse?

Orogenic collapse happens when mountains collapse under their own weight.

Define a craton.

A craton is a stable part of the continental crust that has not been significantly deformed.

What is a shield in geology?

A shield is an area with exposed Precambrian crystalline rock.

What is a cratonic platform?

A cratonic platform consists of sedimentary layers that cover a Precambrian basement.

What is the cause of earthquakes?

Earthquakes are caused by the sudden release of accumulated stress along faults.

What are seismic waves?

Seismic waves are energy waves that radiate from the hypocenter during an earthquake.

Define hypocenter.

The hypocenter is the subsurface origin point of a rupture during an earthquake.

What is the epicenter?

The epicenter is the surface location directly above the hypocenter.

What is stick-slip behavior in geology?

Stick-slip behavior occurs when rocks resist motion and then suddenly slip, releasing energy.

What is a recurrence interval?

The recurrence interval is the average time between similar earthquakes.

What are P-waves?

P-waves are primary, compressional, and the fastest seismic waves.

What are S-waves?

S-waves are secondary shear waves that cannot travel through liquid.

Describe surface waves.

Surface waves travel along the Earth's surface and cause the most damage during earthquakes.

Define the Moho.

The Moho is the boundary between the crust and mantle, detectable by seismic reflection.

What is the P-wave shadow zone?

The P-wave shadow zone is an area where P-waves are refracted by the core.

What is the S-wave shadow zone?

The S-wave shadow zone is an area where S-waves cannot pass through the liquid outer core.

What is a seismograph?

A seismograph is an instrument that records ground motion.

How do you locate an epicenter?

To locate an epicenter, three seismic stations are used along with P–S arrival times to triangulate.

What is earthquake intensity?

Earthquake intensity measures the severity of ground shaking and damage.

What is earthquake magnitude?

Earthquake magnitude is the measure of total energy released during an earthquake.

What is the moment magnitude scale?

The moment magnitude scale is the most accurate measure of earthquake size, based on rupture area and slip amount.