Tectonic Plates

Ch. 7 Notes
Inside the Earth
The Composition of Earth:
o _________: outermost layer of Earth
o 5-100 km thick
o 2 types of crust:
 ____________________: composition similar to granite(30 km thick)
 ____________________: composition similar to basalt (5-8 km thick)
o Mantle: layer of Earth between crust and core.
 ___________ of Earth’s mass
 2,900 km thick
o The Core:
 Mostly iron with smaller amounts of nickel, _________, and oxygen.
 33% of Earth’s mass
 Slightly larger than _________________.
Tectonic Plates
 Are ___________ of the lithosphere that move around on top of the
 Wegner’s theory of continental drift explained many puzzling facts, including
the fit of the Atlantic coastlines of South America and Africa.
 Today’s continents were originally joined together in the ancient continent
 The process of ridge push, convection, and slab pull provide some possible
driving forces for plate tectonics.
 Tectonic plate _____________ are classified as convergent, divergent, and
o Convergent Boundary:
 Where plates __________________.
 ex. The Mariana Trench
o Divergent Boundary
 Where plates ____________.
o Transform Boundary
 Where plates _________________________________.
 Data from satellite tracking indicate that some tectonic plates move up to
_____ cm a year.
Theory of Plate Tectonics
 Theory that the Earth’s lithosphere is divided into tectonic plates that move on
top of the ____________________.
 What causes the plates to move?
o _____________ is the hot material deep within the Earth rising to cool.
o Like a big lava lamp!
Deforming the Crust
 When rocks change shape due to stress, the reaction is called deformation.
 2 types of stress:
o _____________: when objects are squeezed or collide together.
o _____________: when objects stretch or diverge apart.
 Occurs when rock layers bend due to __________.
 _______ types of folds:
o Anticline
o ___________
 Surface along which rocks break and slide past one another.
 ______________________: hanging wall moves down relative to the footwall.
 ______________________: hanging wall moves up relative to the footwall
(reverse of normal fault)
 ______________________: occur when opposing forces cause the rock to
break and move horizontally.
Mountain Building
 When tectonic plates converge 3 major types of mountains are made.
o _______________________: form when rock layers are squeezed together
and pushed upwards.
o _______________________: form when normal faults cause large blocks
of Earth’s crust to drop down relative to other blocks.
o _______________________: form when molten rock erupts onto Earth’s