Geology Exam 3

Liquefaction

Liquefaction

transformation of a granular material from a solid state into a liquid state; three requirements: loose granular sediment, saturation of the sediment from water, strong shaking

Lateral Spread

liquefaction of a subsurface layer; low slope 0.3-3 degrees; 10s of meters

Flow Failure

most catastrophic liquefaction; slope > 3 degrees; 10s of meters - 10s of miles

Ground Oscillation

liquefaction; slope is too gentle to permeate lateral movement; fissures open and close; sand boils up out of the grownd

Cause of Tsunamis

undersea disturbance, usually earthquakes on the seafloor

Character of Tsunami Waves

wavelengths up to 60 miles, can reach speeds of over 400mph, height changes as it approaches land, strip the beaches, cause flooding, destroy buildings, slow down as they reach land and commonly appear as a rapidly rising tide

Tsunami Safety Rules

earthquake is a natural tsunami warning, get to high ground; typically a series of waves not just one; they don’t issue false alarms; never go down the shore to watch

Tsunami Warning System

detects, locates, and sends out warnings to locations around Pacific Ocean, tide gauges and seismic stations, DART (deep ocean assessment and reporting of tsunamis) stations around Pacific and measures water pressure

Indonesian Tsunami and Earthquake

December 26, 2004; M9.0 earthquake off West Coast of Northern Sumatra; Java Trench (convergent plate boundary); over 230,000 killed across 14 countries; shaking lasted 10 minutes; waves began crashing within 15 minutes; two hours later hit India, 7 hours later hit Mauritius and Africa

Japanese Tsunami and Earthquake

2011, M9.03 earthquake; 70 km east of Oshika Peninsula; 15,882 deaths; 435mph up to 6 miles inland, lots of people lost power and fires started, destroyed the nuclear powerplant

Tectonic Setting of Western North America

Convergent off the coast of Alaska, Washington, and Oregon, Transform boundary in California

Origin of San Andreas Fault

a portion of the East Pacific rise was subducted under California creating a transform fault, some parts of the fault are locked with lots of friction, in the week or creeping parts, many earthquakes occur; majority of the fault is locked

1964 Great Alaskan Earthquake, plate tectonic setting

convergent boundary

64 Alaska cause

major subduction movement, Pacific plate moved under North American plate by about 30 feet

64 Alaska length of shaking and magnitude

M9.2 earthquake (2nd largest recorded); 4 minutes of shaking

64 Alaska types of damage

III - X on Mercalli scale, damage covered about 130,000 sq km, 131 killed, 122 of them killed by the tsunami, 16 killed in Oregon and California, large section of City of Seward slid into the ocean due to liquefaction

64 Alaska Aftershocks

thousands of aftershocks recorded in the months following, in the first day 11 smaller earthquakes were recorded

1906 San Francisco cause, length of shakings, magnitude, types of damage, foreshocks, aftershocks

265 miles of fault ruptured; M8.0; intensity from VII - IX; 60 seconds of shaking; 30 seconds before major shaking a small foreshock was felt; horizontal offset of about 20 feet; > 3,000 deaths, most damaged caused by the fire (80% of the city was burned down)

1989 San Francisco Earthquake cause, length of shakings, magnitude, types of damage, foreshocks, aftershocks

M7.0; 60 miles south of San Francisco; first major rupture since 1906; 25 miles of fault ruptured; intensity VI - IX; aftershocks M5.2 after 2.5 minutes and thousands of smaller quakes in the next couple of weeks; 11 seconds of shaking; 67 deaths; liquefaction around bay area; most people killed were on the double decker highway of I-880

Hydrologic Cycle

Evaporation, Precipitation, Return to Oceans

Porosity

the parts of rock or soil that are not occupied by solids, groundwater occupies porosity; Intergranular (space between sedimentary rocks); Fracture (cracks in the rocks)

Sink Holes

solution cavity that opens to the surface

Ground Water

all the water contained in spaces within rocks and soil; originates from precipitation

Surface Water

streams and lakes; originates from precipitation

Karst Topography

a landscape dominated by sink holes

Recharge and Discharge Zones

Recharge - where water enters the aquifer; Discharge - where water flows out of the aquifer

Water Table

the top of the saturated (phreatic) zone in an unconfined aquifer; line between saturated and unsaturated areas; shape changes mimicking the ground surface; moves up and down depending on rain

Groundwater Flow

moves through the porosity in rocks and soil; flows from high to low pressure; can flow uphill; flows down potential/pressure

Potential Surface

pressure surface created by differences in elevation of the water table

Cone of Depression

a conical depression in the potential surface

Springs

a place where groundwater discharges at the Earth’s surface

Confined Aquifer

an aquifer with an impermeable layer above it

Unconfined Aquifer

aquifer that is open to receive water from the surface

Potential Surface Map

lines connect points of equal potential, shows the shape of the pressure surface; ground water flows perpendicular to lines of equal potential

Streams

the part of the hydrologic cycle that returns water to the oceans on the land’s surface; made up of water and sediments

Tributaries

the collection system; a dendritic pattern of smaller streams that feed into the main trunk; number decreases downstream; “v” downstream

Main Trunk

transports the water, enormous drainage basins composed of many smaller sub-drainage basins

Delta

the dispersing system; where the water flows into a standing body of water

Longest Rivers

Nile - 4,132 miles Amazon - 4,000 miles Yangtze - 3,915 miles

Stream Gradient

decreases downstream (relief of the land/slope)

Velocity Patterns

decreases downstream

Stream Discharge

volume of water per time that passes through a stream; velocity x cross sectional area = discharge; velocity = feet/second; cross sectional area = width x depth

Hydrograph

a graph that shows discharge over time

U.S. Rivers Discharge Map

map of real-time streamflow compared to historical streamflow for the day of the year

Drainage Basin

land area from which all precipitation flows to a single stream

Headward Erosion and Stream Piracy

erosion that expands drainage basins, stream piracy - when one stream intersects another and makes it one big one

Suspended Load

particles that are carried within the stream (fine grained - silt and clay)

Bed Load

particles that slide, roll, or bounce along the bottom of the stream (coarse grained)

Dissolved Load

atoms surrounded by water transported by the stream

Floodplain

the portion of a river system that is covered by water during flood stage

Meander

a winding course of stream bends; they migrate throughout the floodplain; erode and flatten out the continent; erode on outside of bend and deposit on inside

Entrenched Meander

rapid uplift of the land causing rapid down cutting

Point Bar

sand or gravel deposited on the inside of a meander bed (deposition)

Cut Bank

the steep walled part of the outside of the meander (erosion)

Oxbow Lake

isolated meander loops, form when a stream cuts through a meander neck

Natural Levee

a curvy-linear mound of sand and gravel that parallels the riverbank

Aquifer

a body of permeable rock saturated with water; water well target

Aquitard

an impermeable body; opposite of aquifer

Solution Cavity

large pores formed by the dissolution of rock; usually forms in limestone (caves)

Permeability

the ability of material to transmit water; grains size influences permeability

Spatial Distribution of Earthquakes

80% originate in circum-pacific belt (The Ring of Fire), 15% originate in Mediterranean-Asiatic belt, remaining earthquakes occur on ridges and scattered through the plates

River System

a network of connecting channels through which water is transmitted back to the oceans

Artesian Well

a well drilled into a confined aquifer with hydraulic pressure for the water to flow to the surface without pumping, the pressure surface is above the land surface

Alluvial Fan

semicircular deposit of coarse sediment formed where the stream gradient suddenly changes

Lake

large inland body of standing water that occurs in topographic depressions

Origins of topographic depressions

1 - melting blocks of glacier ice make kettle lakes 2 - volcanic eruptions 3 - in faults

Oligotrophic Lakes

poorly nourished, not many nutrients, few plants, abundant O2

Eutrophic

highly nourished, high nitrogen and phosphorus input, lots of algae/aquatic plants; algae die and decompose, animals die