GEO EXAM 3 Flashcards
Flow failure occurs at:
A slope > 3º
The west coast of North America is comprised of what 2 plate boundaries? (Alaska & California)
Convergent boundary of Alaska, Transform boundary in California (strike-slip)
A portion of the East Pacific Rise was
Subducted under California
As the Atlantic basin opened, North America…
Moved westward into pacific basin
When and how did The Great Alaskan Earthquake occur
1964, pacific plate moved northwestward and subducted under the North American plate
The Great Alaskan Earthquake magnitude:
9.2
Characterize of the San Andres Fault
Some parts locked (>7) , some parts creeping (weak, 5-6), Earthquakes occur in clusters, separated by long periods of quiescence
Epicenter of Alaskan Earthquake
Prince William Sound, 75 miles east of Anchorage Alaska
Intensity of Alaskan Earthquake
3-10, felt over 700,000ft of Alaska and Canada
Duration of Alaskan Earthquake
4 Minutes
Aftershocks of Alaskan Earthquake
In the first day, there were 11 smaller earthquakes > M 6!
Cause of the Alaskan Earthquake
NW motion of the Pacific plate of about 5 to 7 cm/yr, compression relieved by sudden SE motion of the portions of the Alaskan coast back over the subducting slab, pacific plate moved under the north american plate by 30ft/4min
Effects of Alaskan Earthquake
Montague Island was raised by 25 feet, quarter mile of the seafloor lifted above sea level, Portage was dropped by 9 feet
Damage of Alaskan Earthquake
Landslides, avalanches, liquefaction, tsunamis, and extreme ground shaking, 122/131 were killed by the tsunami (16 in oregon/cali), Low population density, holiday, wooden buildings survived shaking
Tsunami of AE height
12 ft
Liquefaction of AE
Flow failure occurred in Seward
Seismic waves of AE
Texas and Louisiana felt it with 4in of vertical motion and sunk boats
The Great 1906 San Fransisco Earthquake
265 miles of fault ruptured, locked segment, depth of 12.5 miles
Magnitude of SFE 06
8
Intensity of SFE 06
7-9, shaking was more intense in areas of weak consolidated materials around the bay
Duration of shaking for SFE 06
60s for 10-25ft to slide past eachother
Foreshock of SFE 06
Small earthquake felt 30s before
Ground Movement of SFE 06
horizontal offset on the surface was about 20 feet
Damage of SFE 06
> 3K deaths, 225K homeless, 28K buildings destroyed, FIRE WAS MOST OF DAMAGE
The World Series Earthquake 1989
Loma Prieta, just before Game 3
Location of WSE
60 mi from San Fran, 25 miles ruptured
Magnitude of WSE
7.1
Intensity of WSE
6-9
Aftershocks of WSE
M 5.2 aftershock occurred 2.5 min after the main shock, thousands of smaller quakes occurred in the next two weeks
Duration of shaking for WSE
11s
Damage of WSE
67 deaths, 4K injured, 12K homeless, most people killed on a section of highway I-880 that collapsed
Tectonic setting of California
North American plate is sliding SE of the Pacific plate
The Hydrologic Cycle
Evaporation, Precipitation, Return
Three types of porosity
Solution cavities, intergranular porosity, fracture porosity
Solution Cavities
Large pores formed by the dissolution of rock - usually forms in limestones
Sinkholes
Solution cavity that opens to the surface
Karst Topography
Solution cavities create caves, landscape dominated by sinkholes
Permeability
ability of material to transmit water, highly permeable = transmit water quickly, Shale fracking increases permeability allowing the oil and gas to flow out of the rock
Groundwater flow
Moves with pressure to where water table is low, FLOWS DOWN POTENTIAL, originates from precipitation
Potential Surface
Differences in the elevation of the water table creates a pressure surface (in unconfined aquifers the potential surface is the water table)
Cone of Depression
a conical depression in the potential surface
The shape of the water table
Mimics the grounds surface and moves with rain
What is the direction of groundwater flow for FL?
All directions from central FL
Stream
the part of the hydrologic cycle that returns water to the oceans on the lands surface
Two components of streams
Water and sediment
Drainage Basin
an area from which all precipitation flows to a single stream
Parts of a river system
Tributaries, Main Trunk, Deltas
Tributaries
collection, a dendritic pattern of smaller streams that feed water into the main trunk
Main Trunk
Transports water
Spring
A place where groundwater discharges at the Earth’s surface
Deltas
Disperse, river water flows into a standing body of water
The number of tributaries decrease:
downstream
Tributaries V:
downstream
Longest rivers in the world:
Nile (4132), Amazon (4000), Yangtze (3915)
Longest rivers in US:
Missouri (2540), Mississippi (2340), Yukon (1980)
The stream gradient decreases:
Downstream (relief of land)
Stream competence decreases:
Downstream (grain size)
Discharge INCREASES:
Downstream
Discharge
V/t that passes through a stream
Stream discharge=
Velocity x Cross Sectional Area
Hydrograph
a graph that shows discharge over time
Floodplain
The portion of a river system that is covered by water during flood stage
Build house on
TERRACE
Meander
a twisting winding course of looping stream bends, erose outside, deposit inside
Entrenched Meander
rapid uplift of the land causes rapid down cutting
Point Bar
Sand or gravel deposited on the inside of a meander bend
Cut bank
Steeped wall on the outside of the meander
Oxbow Lakes
Isolated old meander bends
Natural levee
a curvy-linear mound of sand and gravel that parallels the riverbank
Alluvial fan
semicircular deposit of coarse
sediment formed where the stream gradient
suddenly changes
Lakes occur in
Topographic depressions
Origins of topographic depressions
Glaciers (kettle), Volcanoes, Faults
Two types of lakes
Oligotrophic and Eutrophic
Oligotrophic
Poorly-nourished, few plants and a lot of O
Eutrophic
Well-nourished, high Nitrogen and Phosphorus output (unhealthy)
When algae dies…
Oxygen depletes
Floods
The inundation of normally dry land resulting
from the rising and overflowing of a body of
water
July 2021 European Floods killed:
242
Floods occur when
Stream channels cannot contain the discharge
Base flow
A portion of the stream flow that is not runoff; it is
water from the ground, flowing into the channel
Lateral spread occurs at
0.3 to 3º
Ground Oscillation
Slope is too gentle to permit lateral movement
Blocks of soil may decouple and begin to shake
Fissures open and close
Sand boils up out of the ground
Tsunami
A series of sea-waves generated by an undersea disturbance
Causes of Tsunamis
Earthquakes, landslides, volcanic eruptions, explosions, and meteorite impacts MOST COMMON IS VERTICAL DISPLACEMENT OF SEAFLOOR
When a tsunami approaches land it:
slows down, amplitude increases
Tsunami Warning System
UNESCO 2006, consists of 25 seismographic stations and tidal gauges (DART)
The Indian Ocean Tsunami
Deadliest tsunami ever, 230,000 killed across 14 countries, earthquake was 9.1 (3rd largest) and shook ground for 10 min
East Japan Earthquake (2011)
9.03 (5th largest), Earthquake moved Honshu 8ft to the east, 15,882 dead and 6,142 injured, Sendai got 6mi inland
