Geology 106 - Exam #2

Groundwater

Water that moves slowly through rock and sediment. A body of sediment/rock that holds lots of groundwater is Aquifer (50% of Long Beach's water is from deep aquifer)

Soil Profile

A series of layers based on weathering and humus content tends to vary from one place to another

Edges of plate are very active and Recognized based on:

1) Earthquake Activity *** 2) Volcanic Eruptions 3) Mountain Ranges 4) Ocean Trenches

Soil -1

45% Detritus, 5% Humus, 25% Air, 25% Water Enables humans to grow crops Soil acts as an interface of the four sphere of the Earth Systems

Root Wedging

As trees grows larger, so do their roots, wedging apart rocks Natural Environment: anywhere trees grow, coastal plains, and local mountains

Sub Soil

B & C Horizon Mostly Detritus, often red in color due to chemical weathering (B) Bed Rock (C)

Chemical Weathering

Breaking of bonds holding minerals together

Body Waves

Can travel through Earth's interior/body. These waves change velocity as they pass through layers of higher density (speed up) and through layers of lower density (slow down)

Stream

Coherent flow of water at Earth's surface, confine within a channel. Water flows due to gravity. Streams alter landscapes Streams erode downward into underlying rocks because they transport load - sediment acts as an abrasive, causing stream (sand and gravel) to deepen its channel

Mass Wasting Type: Slide

Coherent mass of rocks slides down slope along a fracture or sedimentary layer. 1) Rock Slides - slab of rock breaks along a joint 2) Slump - removal of base of a slope forms a fracture along which rocks can move (where streams or waves: La Conchita, Sunken City)

Soil

Combination of loose rock/mineral (detritus) and organic matter (humus) that supports the growth of plants.

Types of Convergent: Collision

Continental crust collides with continental crust. Tall mountains with deep roots Asia vs India began 50 MYA

Plate Tectonics: Convection

Convection in the asthenosphere causes overlying plates of lithosphere to move (tectonics = to move)

Mass Wasting (landslides)

Down slope movement of rock and sediment due mainly to pull of gravity. 1. Can occur on small to large scale and from slow to high velocity 2. M.W event can be triggered by an earthquake, heavy rainfall, oversteepening of a slope or removal of slope vegetation.

Significant Land Forms: Levees

Elevated ridges parallel to stream channel formed as a flood begins, with excess flow kicking out sand and gravel from channel

Seismic Waves

Energy released from rocks that have ruptured

Types of Plate Boundaries: Transform (Fracture Zones)

Exist to transform one plate boundary to another. Produce low to medium magnitude earthquakes, no volcanism Clipperton Transform Boundary San Andreas Fault cuts trough continental crust

Erosional Land Form: Waterfall

Most form where water flows over a ledge of resistant rock (Iguazu and Niagara Falls)

Erosional Land Forms: Valleys

Formed by a combination of stream down cutting and mass wasting . Mass Wasting is keeping pace with down cutting.

Significant Land Forms: Delta

Forms as a stream flows into a standing body of water (lake or ocean) streams load settles rapidly forming a wedge of sediment (Mississippi River Delta)

Soil Texture: Sandy

Mostly sand, porous, water percolates rapidly Natural Environment: deserts, beaches

Surface Waves

Move by a combination of vertical and horizontal shear through solids. Very slow (700 mph) with great wave amplitude

Top Soil

O & A Horizon Surface mostly humus (O) Detritus and Humus Organic (A)

Joint Fractures

Joints allow water to percolate underground promoting chemical weathering (unloading)

Plate Tectonics

Lithosphere plates move due to the transfer of heat from Earth's center to the surface.

Plate Tectonics

Lithospheric plates move in different directions, at different rates, controlled by convection

Soil Texture: Clay Rich

Lots of clay, dense, forms clods Natural Environment: river valleys, valleys surrounded by silicate rich minerals

Soil Texture: Organic Rich

Lots of humus, which absorbs, great for plants

Erosional Land Form: Canyon

Mass Wasting dos not keep pace with downcutting

Magnitude Scale

Measures earthquakes intensity based on S Wave amplitudes (Richter Scale) and now based on amount of fault rupture (Moment Scale) Note: The scales are calibrated together so still essentially refer to same earthquake intensity Magnitude 3 is 32x greater than magnitude 2 (4 x 32 x32 greater 1024)

Types of Convergent: Subduction (Trenches)

Oceanic crust is forced beneath another plate. Melting and recycling of subducted crust produces explosive volcanic eruptions. Andean Subduction Japanese Subduction

Physical Weathering

Physical breakdown of rock at the surface. It increases the surface area for chemical weathering to work on

Types of Plate Boundaries: Convergent

Plates move toward each other compressing the crust, forming mountains experiencing high magnitude earthquakes and major mass wasting events

Types of Plate Boundaries: Divergent (Ridges)

Plates pull apart, producing tension in crust. Low magnitude earthquakes are common, lots of volcanism Mid Atlantic Ridge Salton Trough (brand new plate) - extension of the East Pacific Rise

Unloading

Removal of rocks on top of deeply buried rocks allows them to expands to perpendicular directions of unloading

Mass Wasting Type: Flows

Rocks and sediment move down slope as a thick mixture (water always present) 1) Debris Flow - moves rapidly due to high water content such as after after wildfires) a) Lahar - water mixes with volcanic ash (Indonesia, Japan, Andes Mountains) 2) Earth Flow - slow, variable movement controlled by rainfall and earthquakes (La Conchita, Palos Verdes Peninsula) 3) Creep - very slow down slope movement, usually just the top foot or soof soil.

Mass Wasting Type: Fall

Rocks break free from a slope, falling and bouncing to the base of the slope forming Talus Environment: mountains and canyons

Weatherine

The physical and chemical destruction of rocks and minerals exposed to water, weak natural acids, changes in temperature, and biological activity

Plate Tectonics

Theory explains how and why huge plates of the lithosphere of processes and fractures within Earth's interior with our understanding of major surface processes and features

Plate Tectonics: Convection

Through liquids, heat transfers, rising of heated liquid promotes sinking of cooler, denser, liquid, establishing movement of atoms

Plate Tectonics: Conduction

Through solids, heat transfers. Atom to atom communication of heat.

Secondary Waves (S Waves)

Travel by vertically shearing through solids. Don't pass through gases or liquids. Velocity = 7,000 mph

Earthquake

Vibration of earth's crust due to sudden movement of rocks along a fault (fracture along which rocks move) or due to upward movement of magma within crust.

Chemical Weathering: Dissolution

Water and weak natural acids dissolves rocks. This works fastest on ionically bonded minerals like halite and calcite

Chemical Weathering: Hydrolysis

Weak natural acids like carbonic acid contain an excess of H+ atoms which can substitute for larger atoms (Si, Fe, Ca, K) atoms in silicate minerals. This reduces minerals integrity causing it to fall apart. Converts silicate minerals into clay.

Mercalli Scale

based on what people experienced (observed) during an Earthquake and on damage to structures

Frost Wedging

liquid water seeps into rock fractures, then freezes, expanding by 9% in volume, wedging apart rocks Natural Environment: mountains

Significant Land Forms: Floodplain

low lying areas next to a streams channel that are covered with water during a flood event

Earthquake Effects: Indirect Effects

occur during an earthquake 1. Fire - can occur as natural gas lines break, producing explosive fires (San Francisco, 1906) 2. Liquefaction - vigorous shaking of water saturated sediment turns solid sediments into thick, viscous liquid, pudding like (Mexico City 1985) 3. Mass Wasting - occurs due to shaking of an unstable slope (Turnagain Heights - Anchorage Alaska 1964) 4. Tsunamis - fast and large ocean waves formed as ocean crust is uplifted along a fault, displacing water which becomes the tsunami. The uplift also produces an earth quake. They are co-incidents (Japan 2011)

Chemical Weathering: Oxidation

oxygen interacts with metallic minerals, causing them to rust.

Earthquake Effects: Direct Effects

produced by the seismic, especially the surface waves

Elastic Rebound Theory

rocks underground along a fault become elastically deformed. One fault ruptures, energy is released in all directions (earthquakes) 1) Rebounding effect releases SEISMIC energy 2) Aftershocks - occur after the initial earthquake and are lower in magnitude. They occur because rocks along a fault take decades to adjust to reduce stress levels after a major earthquake event. (Northridge 1994) > 100,000 aftershocks 3) Earthquake Focus - Where seismic energy is first release as rocks rupture a fault. 4) Earthquake Epicenter - Point on Earth's surface directly above the focus.

Primary Waves (P Waves)

travel by compression/expansion of materials so can travel through solids (12,000 mph), liquids (4,000 mph, or gases (740 mph)