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Science chapter 12.2
Terms in this set (45)
What is the lithosphere and where is it found?
it is the made up of tectonic plates and it is floating on the asthenosphere
-the earth's outermost layer
-continental crust is made from granite
-oceanic crust is made from a rock called basalt
-earth's thickest layer
-mostly solid and os further divided into the upper and lower mantle
-upper mantle: partly molten rock containing iron and magnesium. The magma flows like thick toothpaste.
-lower mantle: upper and lower mantle are separated by the transition zone. It is made of solid, dense materials that contains the elements magnesium and iron
The outer core
-layer below the mantle is the outer core
-it is made of liquid, unlike the other layers
-composed of iron and nickel
The inner core
-at the earth's centre
-composed mainly of iron and nickel
-the incredible temperatures at the core keep it solid
-scientists believe that the inner and outer cores rotate at different speeds and may responsible for Earth's magnetic fields.
Why is the temperature in the asthenosphere different throughout?
because of large quantities of radioactive elements
What is mantle convection?
it is when the hotter and less dense material in the mantel rises, cools, and then sinks again, only to be reheated.
Currents in the asthenosphere _____the tectonic plates
if a spreading centre of earth's surface is under water, what is it called?
it is called a rift valley
What is the process of magma cooling as it reaches the surface and becomes new rock?
What is subduction?
the action of one plate pushing below another
when does subduction take place?
when a dense oceanic plate collides with a continental plate, the heavy oceanic plate will dive deep under the lighter continental plate
What usually takes place in subduction zone?
large earthquakes and volcanic eruptions
What is happening in slab pool?
it is when a tectonic plate subducts deep into the mantle, and pulls the rest of the plate with with it.
What is a plate boundary?
the region where two tectonic plates are in contact
What are the three types of plate interaction?
What is happening when plates are diverging?
they are spreading apart. Examples are rift valleys and sea floor spreading
What are the three types of convergent plate boundaries?
oceanic-continental, oceanic-oceanic, continental-continetal
Describe oceanic-continental plate convergence
when a dense oceanic plate collides with a continental plate, the oceanic plat is forced to slide beneath the continental plate forming a deep underwater valley called a trench
what is a volcanic belt?
a long chain of volcanoes
what does the force of collision between oceanic and continental plates create?
mountain ranges as the continental rock crumples and folds.
what happens when the great forces of the tectonic plate movement gets to hard to resist?
what happens when two oceanic plates collide?
cooling will cause one plate to be denser than the other and the denser plate will slide deep into the mantle
what kind of volcanoes are produced when two oceanic plates collide?
volcanic island arc
what happens when two continental plates collide?
both plates are of equal densities so subduction does not take place. As the rocks collide there edges fold and crumple creating mountain ranges.
what happens in transform plate boundaries?
convection currents in the mantle often cause tectonic plates to slide past each other. Since rock slides past rocks, no mountains or volcanoes are formed.
what could a transform plate boundary potentially create?
earthquakes and faults which are breaks in rocks layers due to movement on either side
what is the term used for a fault that is created by a transform plate boundary
what happens when the amount of energy to move tectonic plates along the asthenosphere becomes two hard?
what is the focus?
the location inside earth where an earthqauke starts
what is epicentre?
the point on earth's surface directly above the focus
how do scientists classify earthquakes?
according to the depth of the foci
what is seismology?
the study of earthquakes and seismic waves
what are L-waves or surface waves?
-travels along the earth's surface
-like ripples in a pound
what are primary waves?
-type of body wave
-squeezes and stretches in direction of wave travel
-travels through solids, liquids, and gasses
what are secondary waves?
-type of body wave
-ground motion is perpendicular to direction of wave travel
-travels through solids but not liquids
how is the movement of body waves affected?
by the composition and depth of the different layers
why are paths of body waves curved?
because of the increasing density with depth in the mantle
What is the device used to measure seismic wave energy?
what kind of record does a seismometer produce?
a record of ground motion called a seismogram
what is magnitude?
the number that rates the strength of an earthquake
what are the three types of volcanoes produced by tectonic plate movement?
what is a composite volcano?
-a cone shaped volcano which is built up from repeated eruptions of ash and lava, which build up layers like layers build up in a cake.
-Magma that forms the volcanoes are is usually very thick.
-As the magma approaches the surface, gas gets trapped below, and pressure builds up. Once the pressure gets too much there is a volcanic eruption. -They are usually found near subduction zones
what is a shield volcano?
-form over hotspots (occurs when a weak part of the lithosphere allows magma to break through)
-less explosive than composite volcanic eruptions because the magma is much thinner
-it looks like shield laying on the ground
-occurs in ocean basins, where the lithosphere is thinner than it is on continents
what are rift eruptions?
-occur when magma erupts through long cracks in the lithosphere.
-lava erupts at spreading ocean ridges or rifts at continental crust
-not very explosive or violent, however they do release large amounts of lava
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