plate tectonics Flashcards
solid nickel and iron
about 1000km thick
inner core
liquid
iron
2000 km thick
outer core
iron-rich Rock
about 3000 km thick
semi-solid
top of mantle called the asthenosphere
mantle
Rock/ crust
maximum thickness is about 100 km
lithosphere
proposed by wegener
noticed shape of continents, mountain ranges animal distribution
continental drift
multiple super continents most recent all land Atlantic Ocean is getting bigger Pacific Ocean is getting smaller
Pangea
made of basalt
dense
oceanic plates
made of granite
less dense
continental plates
crust rests on the mantle
upper mantle is called the asthenosphere
convection currents
partially melted
moves slowly
moves crust
asthenosphere
compression of plates
converge
tension
pull apart
diverge
slide past eachother
transform
ocean plate is pushed under the crust
subduction
occurs when plates collide
boundary
island arc Japan
ocean-ocean subduction.
Andes mountain and volcanoes
ocean-continent subduction
Himalayas and Appalachians
continent- continent
rift zone
new crust is made
ocean-ocean
Rift Valley
continent-continent
new crust is made at the mid-ocean ridge
cooling rock “fossilize” the current magnetic field
seafloor spreading and paleomagnetism
normal polarity
reverse polarity
magnetic reversals
measure distance from ridge to point on sea floor
divide distance by age of rocks
sea floor spreading rates
volcanoes that occur in the middle of the plate
no plate boundaries
ex. Hawaii
hot spots
plate moves
hotspot doesn’t
ground motion caused by a geological event
energy is transferred through the earths crust
3 types of waves are generated
earthquakes
earthquake causes
stress that builds up from the movement of plates
volcanoes
meteor impact
cavern collapse
how many earthquakes occur each year
over one million per year
where do large earthquakes usually occur
along subduction zones
point directly above the focus on the earths surface
epicenter
a break in movement. a sliding of the rocks
fault
in the ground where the break happens or begins
focus
energy builds up in the crust and then eventually cannot absorb anymore so it snaps and breaks
elastic rebound theory
primary waves
compression waves
move very fast
p waves
secondary waves
shear waves
move slower than p waves
do not travel through liquids
S waves
slowest waves travel short distances rolling motion side to side motion cause most damage
L waves
shield
composite
cinder cone
volcanoes
quiet eruptions non-explosive form at hot spots and rift zones basalt Hawaii is made up of these
shield volcanoes
hazards of shield volcanoes
lava flows
gas releases
lahars
opening at the top of any volcano
caldera
very explosive
form along subduction plate boundaries
most explosive
contain layers of ash and lava
composite cones
hazards of composite cones
rain of ash and bombs
deadly gases
lahars
steep
piles of ash
form from high silica content lava
cinder cone
hazards of a cinder cone volcano
very explosive high gas content molten ash bombs no lava flows
compared rocks or fossils to one another
relative time
actual age of a rock or fossil in years ago
absolute time
absolute dates are determined
certain atoms radioactively decay
radiometric dating
238
uranium
40
potassium
14
Carbon
2 protons and 2 neutrons are emitted
alpha decay
1 electron emitted
beta decay
1 electron is captured
electron captured
amount of time it takes for half of the radioactive element or the parent element to decay into stable daughter products
half-life
