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)