Earth Science ch 9 & 11
What evidence supports the theory of plate tectonics?
seafloor spreading
Ferromagnetic molecules in the liquid igneous rocks orient themselves to align with Earth's magnetic field. When the rock cools, the molecules are set in place. Earth's poles swap positions periodically, so molecules form different period have different orientations. In order for this fact to support the theory of plate tectonics, the badns of ferromagnetic molecules with alternating orientations are ______ on either side of a ___________ boundary.
symmetrical, divergent
What does the theory of plate tectonics explain?
the movement of oceanic and continental crust
relate the distance of crust from a mid-ocean ridge (divergent boundary) to the age of the crust.
the younger rock is closest to the mid-ocean ridge, older rock is located near the continent
How are mid-ocean ridges formed?
Diverging boundaries where 2 oceanic plates move apart
What changes would end Earth's tectonic activity?
The Earth's mantle would cool and become solid
What plate interaction is most likely associated with the formation of non-volcanic mountains?
continental plates collide with continental plates
How do mountain ranges support the theory that continents were once joined together?
continents that are now separated were once joined together
What in the mantle drives plate motion?
convection
At what type of boundary does the Himalayan Mountain chain exist?
convergence of continental plates
Compressive forces are associated with what type of plate boundary?
convergent boundaries or colliding boundaries
How is new crust created?
Liquid magma from the mantle rises to the new surface
Oceanic crust is composed mainly of basalt. Continental crust is composed mainly of granite. Why does oceanic crust generally tend to subduct under continental crust when plates collide.
They have different densities/ocean crust is denser than continental crust
When mountains are formed there is an interaction between _______ and _________
asthneosphere, lithosphere
What is a hot-spot in relation to volcano formation?
beginning of volcanic island
What type of plate movement forms a rift valley?
divergent boundary, moving in opposite direction
Describe how density differences cause plate motion
during convection the warm less dense material rises and the cooler more dense material sinks
What were Alfred Wegener's main evidences to support his theory of continental drift?
fossil matching, plats, the shorelines matching like a puzzle piece
What is the main source of heat in the magma that builds mountain chains formed by volcanic eruptions?
heat within the crust and mantle
What characteristics of the asthenosphere helps explain the evidence of crustal-plate motion?
mantle in a semi-liquid and convection currents
What landforms are formed at convergent boundaries
marianas trench
What landforms exist at divergent boundaries?
mid-ocean ridge
What conclusion is supported by the discovery of the same fossils on separate continents?
modern landmasses were once connected
The plate pushed down at the subduction zone is ________ than the other.
more dense
Name the 4 types of faults and the type of stress that corresponds to each
normal faults- tensional stress reverse faults- compressional stress thrust faults- compressional stress strike slip fault- shear stress
How is a volcanic mountain formed at the boundary between oceanic crust and continental crust?
oceanic crust collides with continental crust heating as it subducts