GEO Unit 2

Sedimentary Rocks

Rocks derived through weathering and erosion of pre-existing rocks.

Formation of Sedimentary Rocks

Transport and accumulation of fragmental materials or dissolved products from a source region to a site of deposition.

Composition of Sedimentary Rocks

Made up of biogenic or inorganic materials.

Percentage of Rocks that are Sedimentary

75%.

Types of Sedimentary Rocks

Clastic, Biochemical, Organic, Chemical.

Clastic Rocks

Loose rock fragments cemented together.

Biochemical Rocks

Cemented shells of organisms.

Organic Rocks

Carbon-rich remains of once-living organisms.

Chemical Rocks

Minerals that crystallize directly from water.

Mechanical Weathering

A reduction of size—larger particles becoming smaller particles.

Causes of Mechanical Weathering

Abrasion by flowing ice, water, wind, pressure changes, frost wedging, wetting/drying, roots/burrows.

Chemical Weathering

Reaction between minerals and water to form new minerals and/or dissolved ions.

Wind Erosion

Erosion caused by wind that carves rocks.

Water Erosion

Erosion that forms features like the Grand Canyon.

Chemical Example of Weathering

Carbon dioxide dissolves in water, forming a weak acid (carbonic), that attacks and dissolves rocks.

Gruss

Weathered granite.

Lithification

Process that transforms loose sediment into solid rock through compaction and cementation.

Mature Sediments

Sediments that are well-sorted and well-rounded, lacking in unstable minerals.

Sorting

Measure of the uniformity of grain sizes in a sediment population.

Transgression

Coastline migration upward and rising sea level.

Regression

Coastline migration seaward and falling sea level.

Mass Wasting

Downslope motion of earth's materials by gravity.

Types of Mass Movement

Creep, slumping, lahars/mudflow, debris flow, rockfall/slide.

Creep

Slow downhill movement of regolith.

Slumping

Sliding of regolith as coherent blocks.

Mudflow

H2O-rich movement with fine sediment.

Debris Flow

H2O-rich movement with large rocks.

Lahar

Volcanic mud debris flow.

Landslide

Movement down a non-vertical slope.

Rockslide

Slide of only rocks.

Debris Slide

Slide of mostly regolith.

Angle of Repose

The steepest angle of descent under which a material can remain stable.

Gentle slopes

Act to resist movement due to lower forces.

Protoliths

Pre-existing rocks that undergo geological changes during metamorphism.

Foliation

Planar fabric that cuts through metamorphic rock, formed by the alignment of platy minerals.

Ingredients of Metamorphism

Elevated temperature, pressure, differential stress, and water.

Metamorphic Grade

Measure of the intensity of temperature and pressure conditions leading to alteration.

Elastic Rebound Theory

The theory explaining that stress buildup on rocks leads to elastic deformation and eventual rupture.

Fault

A fracture in the earth's crust that is the locus of relative ground movement or rupture.

Focus of an Earthquake

Point of first fault rupture, located at depth in the crust.

Epicenter

Point on the land surface directly above the focus.

Seismic Wave

Waves generated by an earthquake that radiate away from the source.

P-waves

Primary waves that travel by compressing and expanding the material, fastest seismic waves.

S-waves

Secondary waves that move material back and forth, slower than P-waves, and only travel through solids.

Seismograph

Instrument that records ground motion, depicting earthquake wave behavior.

Seismogram

Data recorded by a seismograph, revealing the arrival times of different seismic waves.

Finding Epicenter Method

Requires data from at least three seismic stations.

Reflection and Refraction of Waves

Reflection is the bounce off a boundary, while refraction is the bending of waves at a boundary.

Low Velocity Zone (LVZ)

Occurs beneath oceanic crust, where seismic-wave velocity decreases.

Strain

Change in shape via deformation caused by tectonic forces.

Compression

Stress that shortens and thickens materials by squeezing.

Tension

Stress that stretches and thins materials as the ends are pulled apart.

Brittle vs. Ductile Deformation

Brittle occurs in shallow crust and fractures the rock, while ductile occurs at higher pressures and temperatures, altering shape without breaking.

Normal Fault

Fault where the hanging wall moves down relative to the footwall, resulting from extension.

Reverse Fault

Fault where the hanging wall moves up relative to the footwall, resulting from compression.

Strike-slip Faults

Faults that occur along boundaries of tectonic plates that slide past each other.

Elastic Deformation

Temporary deformation where rocks return to their original shape after stress is removed.

Moment Magnitude Scale (MW)

The best measure of earthquake size based on several seismic wave characteristics.

Radiometric Dating

Method of dating based on the decay of parent isotopes into daughter isotopes.

Half-life

The time it takes for half of unstable nuclei to decay.

Induced Seismicity

Earthquakes caused by human activities, such as changes in groundwater.

Magnitude vs Intensity

Magnitude measures the size of an earthquake, while intensity measures the damage observed.

Modified Mercalli Intensity Scale

A scale that assigns Roman numerals to different degrees of damage.

Fault Geometry

Classification based on the fault's geometry and motion.

Differential Stress

Stress that causes different responses in rocks, leading to deformation.

Neocrystallization

Formation of new minerals from old ones during metamorphism.

Thermal Metamorphism

Heating caused by a plutonic intrusion.

Orogenesis

The process of mountain building that applies force to rocks.

Seismic Belts

Narrow zones around the globe where most earthquakes occur.

Mafics

Minerals that are less stable at the earth's surface, indicating sediment immaturity.

Evaporite Sediments

Chemical sediments that precipitate in a specific order based on solubility.

Foliation,

Planar fabric in metamorphic rocks due to differential stress.

Mass Wasting Characteristics

Includes types of movement from slow to fast: creep, slumping, lahars/mudflows.

Jointing

Fracturing in rock where no movement has occurred.

Submarine Debris Flows

Movement of sediment that breaks apart as it flows.

Seismic Ray

An imaginary point on a wave front indicating changes in position.

Schist

A type of metamorphic rock with significant foliation, often containing minerals like garnet.

Orogenic Uplift

Uplifting of rocks due to tectonic processes, contributing to landslide hazards.

Rockfall

Movement characterized by vertical freefall.

Joints, Faults, and Folds

Deformation features related to the geological stresses and tectonic activities.

Transitional Metamorphism

Occurs between 250° C and 850° C, where rocks are altered due to pressure and temperature.

Seismic Wave Behavior

Seismic waves provide information about the material they pass through and can indicate sources of earthquakes.

Gravitational Energy

Potential energy due to an object's elevation, contributing to mass wasting.

Pressure vs. Temperature in Rocks

Higher pressure and temperature conditions lead to more ductile behavior in rocks.

Types of Metamorphism

Includes thermal, burial, dynamic, regional, hydrothermal, subduction, and shock metamorphism.

Basic Principles of Geology

Study of earth processes including sedimentation, metamorphism, and tectonic movement.

Angle of Repose for Fine Sand

About 35°.

Angle of Repose for Coarse Sand

About 40°.

Angular Pebbles Angle of Repose

Approximately 45°.

Hazards of Earthquakes

Can be influenced by human activity, local geology, and earthquake magnitude.

Recrystallization

The process where minerals change size and shape without changing composition.

Chemical Weathering's Role

Alters minerals and increases overall weathering through reactive processes.

Submarine Slumps

Movement of blocks in a submerged environment leading to mass wasting.

Earthquake Prediction

Possible in the long term, but not accurately predictable in the short term.

Metamorphic Zones

Regions where index minerals indicate the metamorphic grade of surrounding rocks.

Seismic Wave Propagation

Describes how seismic waves travel through different Earth materials.

Shock Metamorphism

Changes in rocks caused by extreme pressures from impacts.

Hydrothermal Metamorphism

Alteration by the action of hot water.

Seismic Rebound Aftershock

Waves that occur after an initial earthquake as the crust stabilizes.

Sedimentary Layering—Stratified

Fine layering characteristic of sedimentary deposits.