Geology (Midterms) Flashcards
is grounding shaking caused by the sudden and rapid movement of one block of rock slipping past another along fractures in Earth’s crust
Earthquake
fractures in earth’s crust called
faults
it tends to occur along pre-existing faults where internal stresses cause the crustal rocks break into two or more units
earthquake
the location where slippage begins
hypocenter or focus
the point on Earth’s surface directl above the hypocenter
epicenter
a form of energy that travels through the lithosphere and earth’s interior
seismic waves
the energy carried by these waves causes the material that transmits them to shake
seismic waves
The famous San Francisco Earthquake
What energy is released that can generate earthquake - like waves
volcanic eruptions, massive landslides, and meteorite impacts
it have been discovered thousands of meters above sea level
fossils of marine organisms
he conducted a landmark study following the 1906 San Francisco earthquake
Harry F. Reid
it was accompanied by horizontal surface displacements of several meters along the northern portion of the San Andreas Fault
San Francisco earthquake
it keeps the fault from rupturing and slipping
friction resistance
a series of earthquake waves radiate outward as it slides
snap back
numerous earthquakes if lesswe magnitude that ahpoen after the strong earthquale
aftershocks
result from crust along the fault surface adjusting to the displacement caused by the main shock
aftershocks
small earthquakes which often, but not always, precede major earthquakes by days or, in some cases, several years
foreshocks
three types of faults
normal fault
reverse fault or thrust fault
strike-slip fault
block of rock below the fault
foot wall
block of rock about the fault
hanging wall
a fault wherein the hanging wall moves down relative to the foot wall
normal fault
a fault wherein the hanging wall moves up relative to the foot wall
reverse fault
thrust fault
a fault wherein two blocks of rocks slide past one another
strike-slip fault
mos of earth’s strongest earthquakes occur along large faults associated with _
convergent plate boundaries
the convergent plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate forms a extensive fault zone
megathrust fault
faults in which dominant displacement is horizontal and parallel direction of the fault trace
strike-slip faults
gradual displacement
fault creep
are similar to the instruments used in ancient china
seismographs or seismometers
has a weight freely suspended from a support that i securely attached to the bedrock
seismograph
the records obtained from seismgraphs
seismograms
provides useful information about the nature of seismic waves
seismograms
two main types of seismic waves are generated by the slippage of a rock mass:
body waves
surface waves
travel through earth’s interior
body waves
travel in the rock layers just below Earth’s surface
surface waves
body waves are further divided into two types
primary waves or p waves
secondary waves or s waves
are push/pull waves; they momentarily push and pull rocks in te direction the waves are traveling
primary waves
solids, liquids, and gases resists stresses that change heir volume when compressed and, therefore, elastically spring back once the stress is removed
primary waves
it can travel through all these materials
primary waves
these waves “shake” the particles at right angles to their direction of travel
secondary waves
liquids and gases do not transmit
S waves
Two types of surface waves
rayleigh waves
love waves
causes earth’s surface and anything resting on it to move up and down much as ocean swells toss a ship
rayleigh waves
causes earth’s surface to move from side to side
love waves
this motion is particularly damaging to the foundation of structures
love waves
p waves are the first to arrive at a recording station, the S waves, and finally surface waves
s waves have slightly greater amplitudes than p waves, and surface waves exhibit even greater amplitudes
Seismologists use a variety of methods to determine two fundamentally different measures that describe the size of an earthquake:
intensity
magnitude
scale that uses observed property damage to estimate the amount of ground shaking at a particular location
intensity
scale that uses data from seismographs to estimate the amount of energy released at an earthquake’s source.
magnitude
A measure of how an earthquake was felt in a certain locality area
PEIS
phivolcs earthquake intensity scale
developed the first magnitude scale to use seismic records
Charles richter
is calculated by measuring the amplitude of the largest seismic wave recorded on a sesimogram
richter scale - richter magnitude
seismologists now favor this newer scale for measuring medium and large earthquakes
moment magnitude
is calculated by determining the average amount of slip on the fault, the area of the fault surface slipped, and the strength of the faulted rock
moment magnitude
the phenomenon of transforming a somewhat stable soil into mobile material capable of rising towards earth’s surface
liquefaction
major undersea earthquakes may set in motion a series of large ocean waves
tsunami
processes that deform Earth’s crust to create major structural features, such as mountains, continents, and ocean basins.
tectonic processes
continents were once united into a single supercontinent
continental drift hypothesis
single supercontinent named
Pangaea
He suggested that Pangaea broke up long ago and that the continents then moved to their current positions.
alfred wegener
evidences of the continental drift hypothesis
- the continental jigsaw puzzle
- fossils matching across the seas
- rock types and geologic features
- ancient climates
Constructed a map that pieced together the edges of the continental shelves of South America and Africa at a depth of about 900 meters (3000 feet).
SIr Edward Bullard
A small aquatic freshwater reptile whose fossil remains are limited to rocks of Permian age (about 260 million years ago) in eastern South America and southwestern Africa.
mesosaurus
seed fern
glossopteris
Includes the crust and the uppermost, and therefore coolest, part of the mantle
lithosphere
Earth’s strong outer layer
lithosphere
stone
lithos
is a hotter, weaker region in the mantle that lies below the lithosphere
asthenosphere
weak
asthenos
The lithosphere is broken into about two dozen segments of irregular size and shape called
lithospheric plate
plates
Seven major lithospheric plates are recognized and account for 94 percent of Earth’s surface area:
- North American Plate
- South American Plate
- Pacific Plate
- African Plate
- Eurasian Plate
- Australian- Indian Plate
- Antarctic Plate
Intermediate-sized plates include:
- Caribbean Plate
- Nazca Plate
- Philippine Plate
- Arabian Plate
- Cocos Plate
- Scotia Plate
- Juan de Fuca Plate
One of the main tenets of the plate tectonics theory is that plates move as somewhat rigid units relative to all other plates.
plate movement
Three types of plate boundaries:
divergent plate boundaries
convergent plate boundaries
transform plate boundaries
where two plates move apart, resulting in upwelling and partial melting of hot material from the mantle to create new seafloor
divergent plate boundaries
is the longest topographic feature on Earth’s
surface, exceeding 70,000 kilometers (43,000 miles) in length.
oceanic ridge system
Longest mountain range in the world which is underwater.
mid-atlantic ridge
along the crest of some ridge segments is a deep canyon like structure
rift valley
The mechanism that operates along the oceanic ridge system to create new seafloor
seafloor spreading
As the tectonic forces continue to pull apart the crust, the broken crustal fragments sink, generating an elongated depression
continental rift
where two plates move toward each other and the leading edge of one is bent downward as it slides beneath the other.
convergent plate boundaries
Convergent boundaries are also called
subduction zones
Located along the west coast of South America.
peru-chile trench