Combo with "Earth Science 10 Ch. 12.1" and 1 other
Terms in this set (64)
what is the continental drift theory?
theorizes that continents are not in their original positions but have moved around the earth over the millenia
who was the first scientist to think of the continental drift theory?
Alfred Wegener (German geologist)
what was the name of the super continent?
what are the 3 main pieces of evidence used to support continental drift theory?
jigsaw puzzle fit
matching geological structures and rocks
the extent of ancient glaciers and the rock markings they have left behind
how can continents move?
what is the theory of plate tectonics?
it theorizes that the tectonic plates move around above the asthenosphere
define: magnetic reversal
direction of the magnetic field reverses completley
define: normal polarity
when earth;s magnetic poles are similar to its geographic poles
define: reverse polarity
when earth's magnetic poles reverse so that they are opposite to earth's geographic pole
the study of the magnetic properties of ancient rock
who discovered sea floor spreading?
what is sea floor spreading?
as convection currents cause the new magma to rise, the new magma forces apart the hardened material and continually pushes older rock aside
who explained continental drift?
J. Tuzo Wilson
an area where molten rock rises to the earth's surface under a tectonic plate
what are the four layers of the earth?
describe the crust
outer solid rock layer, grantite on land, basalt in oceans
describe the mantle
thickest layer, mostly solid except for the upper mantle being able to flow like 'thick toothpaste'
describe the outer core
composed of liquid iron and nickel
describe the inner core
mostly solid iron, at tremendous temperature and pressure
where is the lithosphere?
crust and upper portion of the upper mantle
where are tectonic plates located?
make up the lithosphere, which floats on the asthenosphere
how many major tectonic plates are there?
about 12, many smaller ones
what are the two types of tectonic plates?
ocean plates - dense basalt rock
continental plates - less dense granite
what is the asthenosphere?
the molten layer of the upper mantle
what is mantle convection?
as magma is heated in the asthenosphere, convection currents form
what are convection currents? (magma)
patters of magma flow in the mantle caused by molten material being heated and becoming less dense, rising, then flowing horizontally before cooling and becoming more dense and sinking to be reheated again
what is ridge push?
magma cools when it reaches the surface, solidifies and is pushed aside as new magma pushes from below
what is subduction?
the action of one tectonic plate pushing below another tectonic plate
denser plates subduct under a lighter one
what is slab pull?
dense, subducting plate material pulls the rest of the attached plate toward the subduction zone and down into the mantle
what is a plate boundary?
where two plates are in contact
what are the three plate boundaries?
what do the plates do at divergent boundaries?
they move away from each other as magma rises between the plates, which cools creating new lithospheric plate
known as spreading plates, sea floor spreading causes plates to seperate in the ocean
what can form as a result of divergent boundaries?
what do the plates do at convergent boundaries, and what are the three types?
plates come together
types: oceanic-continental, ocean-oceanic, continental-continental
describe oceanic-continental plate convergence
the denser oceanic plate subducts under the continental plate, forming a trench
as the subducting plate moves deeper, large pieces melt off and crystallize into new continental plate, or cone-shaped volcanoes can form from magma seeping to the surface
what is an example of a divergent boundary?
what is an example of an oceanic-continental convergence?
volcano belt of North America's west coast, Cascade Mountain Range
describe oceanic-oceanic plate convergence
the cooler, denser oceanic plate will subduct under the less dense oceanic plate
what can form as a result of oceanic-ocean plate convergence, and what are some examples
volcanic island arcs (Ex. Hawaii) deep ocean trench (ex. Mariana Trench)
describe transform plate boundaries
plates slide past each other in the opposite direction, usually found near ocean ridges
single rocks slide past
what forms at transform plate boundaries?
nothing, but earthquakes and faults are very common
what is an example of a transform plate boundary?
San Andreas Fault
the location in the earth where the earthquake originates from
the location on the surface of earth directly above the focus
the study of seismic waves
what do seismic waves help scientists do?
reveal the source and strength of an earthquake, also help learn about the composition and distances of the earth's interior
what are the types of seismic waves, and what order do they arrive in?
primary wave (p wave), first to arrive
secondary wave (s wave), second to arrive
surface wave (l wave), last to arrive
describe p waves
type of body wave
first to arrive
ground squeezes and stretches in direction of wave travel
travels through solids, liquids and gases
describe s waves
type of body wave
second to arrive
ground motion is perpendicular to direction of wave travel
travels through solids, not liquids
describe l waves
travels along earth's surface
last to arrive
ground motion is rolling action (like ripples)
how do you measure earthquakes?
describe seismometers and what they do
early ones just measured whether the ground shook
some measure horizontal movement, others vertical
what is a seismogram?
shows when an earthquake started, how long it lasted, and the magnitude
distance-time graph can reveal the focus
how does the ricter scale work?
1 increase in magnitude = 10x stronger
a magnitude 6 is 100x more powerful than a 4
what does the intensity of an earthquake depend on?
distance from epicentre, areas type of geology
what is liquification? (earthquakes)
process in which the vibration of the seismic waves causes ground water to rise to the surface, turning solid ground into a liquid-like material
what are the 3 types of volcanoes?
describe composite volcanoes
located along subduction zones (convergent plate boundaries)
layers of ash and thick lava form a tall cone
as magma reaches the surface, it cools, hardens and traps gases below, pressure builds and then eruption
what is an example of a composite volcano?
Mount. St. Helens
describe shield volcanoes
not found at plate boundaries, form over hot spots
largest volcanoes, not as explosive
thin lava flows out from a hotspot and forms a low, wise cone
what is an example of a shield volcano?
Hawaiian Islands (chain of volcanoes)
describe rift eruptions
occur along cracks in the lithosphere
not explosive, release massive amounts of lava
what is an example of a rift eruption?
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