APES Geologic Time Scale, Volcanoes, Plate Tectonics, and Earthquakes

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Terms in this set (...)

Info about the Earth's center
available from earthquakes
crust
thin rocky layer on surface, thinner on ocean floor than on the Continent, consists of silicon, oxygen, iron, and magnesium (silicon and oxygen most abundant)
moho discontinuity
boundary about 40 km below surface 7 km on ocean floor
mantle
has 2 sections:
upper mantle- dense, hard rock
lower mantle- more dense rocks b/c pressure
core
2 sections:
outer-liquid probably made of iron and is responsible for magnetic field
inner- solid, consisting of iron and nickel
gutenburg discontinuity
seperates the core from the mantle
movement within the mantle
layers grouped according to consistancy
lithosphere
the crust and upper mantle which floats on asthenosphere
asthenosphere
near top of mantle, has high temps w/ pressure causing small melting of rock (less dense rock rises while others (lower mantle and core) sink)
convection cell
liquids, solids, and gases form cells, bring new rock to crust, evidence suggests entire continent drift on convection cells
origin of earthquakes
convection cells within mantle cause plates to move constantly, when plates slip they cause waves which=earthquakes (most in US along N.A. plate and San Andreas Fault
seismic gap
area where plates stick together, as they try to move pressure builds and earthquakes occur
focus
the source of earthquake, waves travel in all directions below surface
epicenter
area on surface above focus
P-waves (primary waves)
fast moving longitudinal waves, 1st to reach equipment, can travel through any material
S-Waves (secondary waves)
slow moving transverse waves move side to side through solids only
L-waves (surface waves)
interaction b/t P and S waves, cause surface to shake and roll (worst type)
Shadow zone
area in earth not affected by P and S waves becuase of density of material
Seismograph
instrument used to record earthquake, need three locations to locate epicenter
Richter scale
scale to measure size and magnitude of earthquake, measures amount of energy released
Plate boundaries
where plates meet, 4 types
convergent boundry
where either continental or oceanic plates collide. can form different land and ocean features (cont-cont forms large mnts)
Subduction zone
cont-oceanic where oceanic goes under cont, volcanic mnts form on land, oceanic-oceanic forms an island arc of volcanic islands
divergent boundary
2 oceanic plates moving apart forms mid ocean ridge, 2 cont plates moving apart forms a rift on land
Transform fault/stike-slip boundary
2 parallel cont plates moving opp directions (san andreas fault)
ring of fire
area in Pacific ocean marked with many volcanoes and earthquakes
Shield volcano
quiet eruptions, low viscosity lava looks like cone with gentle slope (Hawaiian islands)
Cinder Cone volcano
viscous lava with violent eruptions b/c trapped steam which forms tuffs of ash, cinder, and lapilli (Mexico)
Composite volcano
has variety of lava types and explosions looks steeper than shield but not as steep as cinder cone (Mt. Fuji)
Caldera volcano
eruption of an OLD composite volcano that fills up with water (Crater Lake, Mount St. Helens)
Pahoehoe Lava
low viscosity, little silica and lots of water
Aa Lava
high viscosity, lots of silica and a little water
cc--> <--cc
convergent continental plates, occurs b/t Asia and India, forms: Himilayan mnts.
oc<-- -->oc
divergent oceanic plates pushing apart, occurs middle of Atlantic Ocean, forms mid-atlantic ridge, sea-floor spreading, rift valley
oc--> <--cc
subduction, oc goes under cc, located in Japan and south am. west coast (chilie)
^l lv
transveral/strike-slip boundries, parallel plates moving in opposite directions, where it occurs California, forms San Andreas Fault line
Lithosphere
crust and upper mantle
asthenosphere
magma that sits under lithosphere
convection currents
circular movement of magma
moho
P waves change speeds
primary
push-pull motion
secondary
wave motion
L
circular "rolling" motion
Precambrian
Origin of life on Earth - about 600mya
Paleozoic Era
"Ancient Animal" Era 570-225 MYA
Mesozoic Era
"Middle Animal" Era; The Age of Dinosaurs 225-65 MYA
Cenozoic Era
"Recent Animal" Era; The Age of Mammals 65 MYA to today
Quaternary Period
Age of Hominids (Man and close ancestors) 2-0 MYA
Cretaceous/Paleocene Discontinuity (K-T Boundary):
70% of all animal species become extinct, including most of the dinosaurs. All kinds of living things were affected by this mass extinction, including plants. A large percentage of the plant species on Earth became extinct, including the dominant group of phytoplankton. 65 MYA
Permian Extinction:
During this period of time, 50% of all families of life on Earth became extinct. It is estimated that this meant the extinction of up to 96% of all species. 225 MYA
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