EARTHSCI 1G03 FINAL

Reverse Fault

Movement on hanging wall is up relative to footwall; result of compression

Thrust Fault

Special type of reverse fault with a low-angle fault plane; common in Rockies

Canadian Rocky Mountains

Series of small thrust faults stacked on larger ones; structure varies by rock type and location

Strike-Slip Fault

Horizontal movement only; rocks slide past each other

Folds

Ductile deformation formed under high temperature and pressure

Axial Plane

Imaginary surface dividing the two limbs of a fold

Fold Axis

Line formed by intersection of axial plane with rock layer

Anticline

Fold with convex shape; oldest layers in the center

Syncline

Fold with concave shape; youngest layers in the center

Structural Dome

Circular anticline

Structural Basin

Circular syncline

Relative Age

Age compared to other objects/events (not in years)

Absolute Age

Actual age in years

Relative Dating Principles

Based on rock relationships and fossils (faunal succession)

Correlation (Technique #1)

Matching rock layers by physical characteristics; not always same age

Cross-Cutting Relationships

Feature that cuts another is younger

Stratigraphic Correlation

Uses fossil succession to match rock layers

Index Fossils

Short-lived, widespread fossils used for dating

Unconformities

Gap in sedimentary record; not all layers have been deposited continuously over time

Absolute Dating Method

Uses radioactive isotopes—They are transformed into stable daughter products

Half-Life

Time for half of a parent isotope to decay

Effective Time Range

About 10× half-life for accurate dating

Radiocarbon Dating

Uses C-14 decay to determine age of once-living material

Best Rocks for Dating

Igneous most accurate; sedimentary less reliable

Bracketing

Using igneous intrusions + cross-cutting to determine age

Anthropocene

Proposed human-influenced time period (not officially accepted)

Plastiglomerate

Rock made of plastic + natural materials

Stream Flow

Laminar or turbulent; more velocity = more turbulence

Discharge (Q)

Volume of water flow; Q = A × V

Drainage Basin

Area where water flows into a stream

Drainage Divide

Boundary separating drainage basins

Dissolved Load

Ions dissolved in water (~35%)

Suspended Load

Particles carried in water (most transport)

Bed Load

Particles rolling along bottom

Capacity

Amount of sediment a stream can carry

River Profile

Concave shape of river from source to mouth

Gradient

Steepness (rise/run)

Base Level

Lowest level a stream can erode to

Changing Base Level

Dams create new base level and trap sediment

Braided Streams

Many channels due to heavy sediment load

Meandering Streams

Curving streams with erosion (cutbank) and deposition (point bar)

Flood Probability

1 / recurrence interval (e.g., 100-year flood = 1%)

Magnetic Declination

Difference between magnetic north and true north

Slope Gradient

Rise / run

Latitude & Longitude

Spherical coordinate system

UTM

Grid-based coordinate system

Groundwater Zones

Unsaturated zone, water table, saturated zone

Recharge Zone

Where water enters groundwater

Discharge Zone

Where groundwater exits (lakes, streams)

Effluent Stream

Gaining stream (fed by groundwater)

Influent Stream

Losing stream (loses water to ground)

Porosity

Ability to store water

Permeability

Ability to transmit water

Aquifer

Rock that is porous and permeable

Cone of Depression

Lowered water table around a pumped well

Unconfined Aquifer

Open to surface; easily recharged

Confined Aquifer

Trapped between low-permeability layers

Artesian Well

Water flows naturally due to pressure

Springs

Natural groundwater discharge

Groundwater Pollution

Contaminants spread through flow

Water Extraction Problems

Saltwater intrusion and land subsidence

Saltwater Encroachment

Over-pumping causes saltwater to rise

Land Subsidence

Ground sinking due to groundwater removal

Karst

Landscape formed by dissolving limestone

Mass Movement

Downslope movement of material due to gravity

Angle of Repose

Stable slope angle (~35–45°)

Role of Water

Small amounts increase cohesion; too much increases movement

Mudflows/Debris Flows/Lahars

Fast-moving mixtures of water + sediment

Debris Flow

Poorly sorted material (pebbles to boulders)

Lahars

Volcanic mudflows (water + ash)

Mudslides

Common in tropical settings with deep weather-ing of soils and abundant rainfall, especially common after tropical storms and hurricanes

Creep

Slow downhill movement

Solifluction

Slow flow over permafrost

Rock Falls

Free-falling rock; forms talus

Rock Slide

Movement of bedrock blocks

Triggers for Mass Wasting

Rain, earthquakes, weak structures, human activity

Conditions for Landslides

Weak layers under heavy loads

Repeating Slides

Occur repeatedly if conditions unchanged

Quick Clay

Marine clay destabilized by freshwater

Fossilization Requirements

Hard parts, low oxygen, rapid burial

Preservation Types

Freezing, amber, permineralization, molds, casts, carbonization, trace fossils

Trace Fossils

Evidence of activity (not the organism itself)

Corals

Modern are colonial; ancient could be solitary

Wave Motion

Waves slow and break near shore

Longshore Drift

Sediment moves along shoreline

Cliff Erosion

Waves erode base causing collapse; headlands erode faster

Cliff Features

Sea arches, stacks, and beaches form over time

Inner core

5140-6370 km depth, solid, metallic, spherical core composed of mainly iron and nickel. Seismic waves are sharply reflected at 5140 km depth

4 conditions of a mineral

Naturally occurring, Solid crystalline substances, Inorganic, Definite chemical compositions

Classification of Igneous rock based on

Texture and mineral content

Oceanic crust is mainly

Mafic (basaltic)

Pahoehoe

Ropy, smooth lava that flows easily

aa

blocky lava

Basaltic lava

Low viscosity, can flow long distances

Andesitic lava

Too viscous to flow far

Earthquakes

shock waves, or vibrations within Earth

P waves

Travel through solid and liquid, fastest waves, parallel to movement, series of expansions and compressions

S waves

Travel through solid only, slower than P waves, perpendicular to transport direction. do not penetrate beyond 2900 km

Liquefication

Transformation of saturated sediment to liquid when ground shaking causes particles to lose contact

Ocean crust thickness

2-10 km