GEOL 120 - Midterm 2 Flashcards
Earthquake Magnitude
A measure of the energy released by an earthquake, an earthquake has only one magnitude.
Earthquake Intensity
A measure of the observed shaking caused by an earthquake, one earthquake has different levels of intensity across different locations.
Modified Mercalli Scale
Describes earthquake intensity based on observed shaking severity, has 12 divsions of intesnity.
Moment Magnitude
Measures the energy released by an earthquake based on fault area, rupture velocity, and rock strength.
Richter Scale
Measures earthquake amplitude of the largest seismic wave based on a logarithmic scale. For large earthquakes it is approx equal to the moment magnitude.
Faulting
The lateral motion of two bodies of rock.
Units for magnitude of earthquakes
“M”, they increase 10x per 1 increase.
Active Faults
Faults that have been active in the past 10,000 years.
Strike-Slip Faults
Faults where the motion is parallel to the strike of the fault. Right-lateral if the RHS moves towards you as you look along the fault line and vice-versa.
Dip-Slip Faults
Faults with vertical displacement.
Reverse Faults
Faults with up-dip motion common during mountain building.
Normal Faults
Faults with down-dip motion common in subduction zones.
Focus
The point at which rocks rupture during an earthquake.
Epicenter
The point on the Earth’s surface directly above the focus of an earthquake.
P-Waves
Fastest earthquake waves that travel through push-pull motion.
S-Waves
Slower earthquake waves that travel through side-to-side motion.
R-Waves
Surface waves that travel through rolling motion and are the most damaging.
The Different Types of Faults
Normal, reverse, and strike-slip
How earthquake intensity and magnitude are measured
Intesity is measured based on the 12 level MMI (using seismographs), magnitude is measured based on the Richter scale (amplitude of greatest seismic wave; up to 8M)
Slumps
Motion of large blocks of mass along curved slip planes, common in softer rock or soil.
Slides
Motion of large blocks of mass moslty along straight slip planes, common in rock and soil
Falls
Direct, free dall of rocks fown a steep slope, common in hard rock
Flows
Fluid-like motion of soil, aka soil creep, that is seen through buckling of infrstructure
Slope Stability
Factors affecting the stability of slopes such as earth material, climate, vegetation, and water.
Sinkholes
Depressions in the ground caused by the collapse of surface material into underground cavities.
Subsidence
The sinking of the Earth’s surface due to various factors like fluid withdrawal or subsurface chemical weathering.
Mass Wasting
The downslope movement of rock or soil as a coherent mass.
What type of rock faces produce falls and slumps
Slumps are produced by soft rock, falls by hard rock
How does the strength of rock influence the types of landslides
It affects the internal strength of the slope (slope stability), softer rock tends to slump, while hard forck tend to fall.
What is the relationship between water, climate, and landslides
Climate influences the amount of water that infiltrates the ground and the time of precipitation; water affects slope stability (which leads to landslides) by
(1) developing soil slips by saturating the soil, like during storms;
(2) developing slumps/slides after long periods of infiltration; (3) eroding the base of the slope (4) creating “quick clay”, saturating clay to such a degree it loses shear strength and flows/behaves like a liquid
Ways to predict and manage landslides
Identify areas with high potnetial for landslides, and create stability maps; minimize and remove buildings on unstable slopes; drainage contorl, reducing gradient; slope supports; benching; warning systems.
Safety Factor of Lanslides
The ratio of resisting to driving/sliding forces of a slope.
What influences wave height
wind speed/velocity, duration, and fetch (area over which wind blows)
Surface Currents
Fueled by wind, patterns of surface currents are determined by wind direction, Coriolis forces from the Earth’s rotation, and the postion of landforms that interact with the currents.
Deep Shore Currents
Form from differences in water density (cold, dense water sinks and surface water flows to replace it)
Currents
Horizontal movement of a large volume of seawater due to oblique waves, difference in water temperature, and or differences in water salinity. Can be global or local.
Erosion Shaped Coastlines
Waves expend their energy at the shoreline, as the wave front apporaches the coastline, its shape becomes parallel to the coastline. Waves converge (increase wave height, increased energy) at the rocky points and diverge at beaches. Long-term effect: wave erosion straightens the shorelines.
Berms
Flat, backshore areas formed by deposition from waves expending the last of their energy
Beach face
The sloping portion of the beach below the berm
Swash zone
Part of the beach face exposed by the uprush and backwash of waves
Surf zone
Portion of seashore environment where turbulent translational waves move toward the shore after the incoming waves break
Breaker zone
Area where incoming waves become unstable, peak, and break
Longshore trough & bar
Elongated depression and adjacent ridge of sand produced by wave action
Hard stabilization
Method creating artificial barriers to beach erosions (jetties, groins, breakwaters, and seawalls). often interfere with zig-zag/lateral trasnport of sediment.
Soft stabilization
Approach using beach nourishment, expensive but more natural.
Factors putting coastal areas at risk for natural hazards
Rising sea level, increased erosion, and human interference with natural processes
Beach nourishment
Artificially adding sand to the beach for protection. More natural and aestheically pleasing, protects shorline erosions, provides recreation beach. Expensive, can be eroded quickly.
Jetties
Structures often constructed in pairs at the mouth of a river or inlet, stabilize a channel, control the deposition of sediment and deflect large wave. Cons: block littoral transpot of sediment —> erosion of downdrift beaches and deposition of sediment in the channel
Groins
Linear structures perpendicular to the shore designed to protect shorelines and trap sediment. Pro: widen the beach, protecting from shoreline erosion. Con: erosion downdrift, as groin traps sediment on the updrift side, the downdrift area is deprived of sediment.
Seawalls
Engineering structures constructed at the water’s edge to minimize coastal erosion. Pro: retard erosion, blocks water side infrastructure. Con: not effective at the base of sea cliffss, reduces bioodiversity in the long term.
Breakwaters
Structures designed to protect a beach/harbor from the force of waves. Pro: provides a protected area or harbor for boat moorings. Cons: blocks natural littoral trasport of sediment, creating sand bars.
Tides
Caused by gravitational force acting on the oceans. Magnitude and timing of tides depend on axial tilit, goemetry of basins, air pressure
Waves
Generated by wind blowing over water
Wave base
Depth in a body of water where the action of surface waves stops stirring the sediments, one half the wavelength
Causes waves to break as they approach the shore
The shallower water leads to decreased velocity/wavelength and increased wave height, making waves steeper, before impinging on the bottom
Rip currents
Seaward flow of water in a confined narrow zone from a beach to beyond the breaker zone
Longshore currents
Current of water and moving sediment that develops in the surf zone as a result of waves striking the land at an angle
How to escape rip current
Swim parallel to the shore until you are out of it
Sediment Load
Materials moved by streams
Dissolved Load
ions from mineral weathering
Suspended Load
Fine particles (silt and clay) in the flow
Bed Load
Larger particles roll, slide and bounce (saltation)
Calculating Streamflow
Discharge = streamflow (Q): volume of water transported per unit time
Q = Width * Depth * Velocity
Lowest level that a stream erodes
Sea Level
Lower Base Level
Steeper profile, increases stream erosion. Caused by sea level drop, subsidence at mouth, uplift at head, removing/loss of lakes
Raise Base Level
Shallower profile, deposit sediment. Caused by sea level rise, uplift at the mouth, susidence at head, creation of lakes.
Competence
Maximum size particle transported
Capacity
Maximum load transported
Vegetation and Runoff
Creates a lag time between peak rainfall and discharge, intercepting and slowing precipitation hitting the ground, leading to less flooding and erosion.
Overland Flow / Runoff
Water moving over the surface as overland flow, keeps rivers and lakes full of water, and changes the landscape through erosion
Infiltration
Water that seeps into the surface of the land, helps plant growth and the environment
Factors influecning runoff
Covering land with impermiable surfaces (increases runoff), removing vegetation (increases speed of runoff), fertilizers (pollutes runoff).
How Streams Originate
Moving water forms a channel, channel erodes the substrate, caused by flooding, rain, etc.
1 year, 5 year, and 10 year floods
A flood with a magnitude greater than or equal to X can be expected every 1/5/10 years; it is the recurrence inteval.
How and Why Streams Move in Landscapes
They are a primary erosion agent, cutting banks and point bars.
Oxbow Lakes
An abandon channel filled with water, when the stream cuts out a channel and the channel gets so much sediment that it is cut off from the mainstream (i.e erosion at the outside bend and deposition at the inside bend)
Hydrograph Factors
Slow peak discharge and lag time, influenced by infiltraion and runoff, size of watershed, and land cover
How Urbanization Alters Hydrographs
Decreases lag time and causes peak discharge to increase
Importance of Sediment in Streams
Solid material that is moved and deposited in a new location, helps shape the landscape by transporting sediment, creating natural levees, forming nutrient-rich soils
Water Cycle Components
Evaporation, precipitation, infiltration, and runoff
Aquifer
Earth material capable of supplying groundwater from a well at a useful rate
Aquiclude
Earth material that arrests the flow of liquids; impermeable layer holding water in place, underneath aquifer
Porosity
Percentage of void space in a material
Permeability
Ability of a material to transmit fluids
Hydraulic Gradient
Gradient and pressure of the water table
Hydraulic Conductivity
Ability of a material to transmit fluids, aka permeability
Groundwater Flow Control
Flows from high pressure to low pressure areas, influenced by hydraulic gradient and conductivity
Oasis Formation
Water from recharge areas flows underground to oasis discharge points
Water Distribution System
Mimics artesian aquifers to deliver water to faucets. Water is pumped into an elevated storage tank, creating and artificial pressure surface, driving water through the distribution system.
Cone of Depression
Sag in water table from overpumping, leading to land destabilization and water table lowering, making it more expensive or impossible to pump the water
Subsidence from goundwater pumping
Fluid withdrawal reduces support for overlaying materials
Wetlands
Areas inundated by water, important for coastal erosion buffering and water filtration
Artesian Wells
Groundwater flowing from a confined aquifer under pressure
Wells
A hole dug deep enough that it penetates below the water table, and fillis up with water due to pressure
Springs
Water flowing from the aquifer intersects surfaces
Aquifer Influence
Permeability and porosity impact the rate of groundwater supply
Groundwater Concerns
Overconsumption leads to depletion and quality issues from pollutants
Soil Zones
Unsaturated zone above the water table and saturated zone below
Stream Order
Measure of relative stream size, from first-order tributaries to larger rivers
Evapotranspiration
Sum of water movement processes from land to atmosphere, crucial for ecosystem water balance
Damming Impacts
Prevents natural flooding and levees, affects sediment transport, disrupts ecosystems, and can lead to flooding if dams break
Sediment Transport Importance
Shapes landscapes through erosion, transport, and deposition
Earthquake Precautions
Hazard-reduction programs, warning systems, and building structures to withstand shaking
Earthquake Warning Signs
Microearthquakes, foreshock activity, radon gas emission, and ground tilt.
