Download Are the continents moving? What are plate tectonics?

Plate Tectonics
SPI 0507.7.1 Describe internal forces such as volcanoes, earthquakes,
faulting, and plate movements that are responsible for the earth’s major
geological features such as mountains, valleys, etc
Are the continents moving?
 Alfred Wegener was the scientist who proposed the
Continental Drift Theory in the early twentieth century.
Are the continents moving?
 Simply put, his hypothesis proposed that the continents
had once been joined, and over time had drifted apart.
Pangaea was a supercontinent that included all the
world's landmasses in the late Paleozoic and,
according to the theory of plate tectonics.
Are the continents moving?
What are plate tectonics?
 Scientists developed a theory called plate tectonics to
explain how forces deep within Earth can cause the
ocean floor to spread and continents to move.
What are plate tectonics?
 This theory describes the lithosphere (the crust and
upper part of the mantle) as being made of huge plate
of solid rock. Earth’s continents rest on these plates.
The almost- melted rock of the asthenosphere acts as
a slippery surface on which the plates can move.
What cause the ocean floor
to move?
 The ocean floor between South America and Africa is
spreading at a rate of 4 centimeters (1.5 inches) every
year.
What cause the ocean floor
to move?
 In the middle of the ocean where the plates are moving apart,
magma is pushed up from the mantle to the surface. The upward
movement of magma causes tension, or a stretch or push, on the
plates. This push moves the ocean floor apart and separates the
plate. This is called sea floor spreading. As the hot rock reaches
the surface it cools and builds up equally on both sides of the
opening. The cooling rock forms the mid-ocean ridge.
crust?
 A divergent boundary occurs when two tectonic plates
move away from each other.
crust?
 When two plates come together, it is known as a
convergent boundary.
crust?
 Two plates sliding past each other forms a transform plate boundary.
 http://www.classzone.com/books/earth_science/terc/content/visualizations/
es0804/es0804page01.cfm?chapter_no=08
 http://www.passmyexams.co.uk/GCSE/physics/tectonic-platemotion.html#top
crust?
 A fault is a break or crack in the rock of the lithosphere
along which movement takes place. There are three
types of faults. Strike-slip faults indicate rocks are
sliding past each other horizontally, with little to no
vertical movement.
crust?
 Normal faults create space. Two blocks of crust pull
apart, stretching the crust into a valley.
crust?
 Reverse faults, also called thrust faults, slide one block of
crust on top of another.
 http://www.classzone.com/books/earth_science/terc/content/
visualizations/es1103/es1103page01.cfm
How are mountains created?
 Slow but gigantic movements of the earth’s crust form
mountains. Fold mountains are formed when two plates
collide head on, and their edges crumbled, much the
same way as a piece of paper folds when pushed
together. Example: The Himalayan Mountains were
formed when India crashed into Asia and pushed up
the tallest mountain range on the continents.
How are mountains created?
 Fault block mountains form when faults or cracks in the
earth's crust force some materials or blocks of rock up
and others down. Instead of the earth folding over, the
earth's crust fractures (pulls apart). It breaks up into
blocks or chunks. Sometimes these blocks of rock
move up and down, as they move apart and blocks of
rock end up being stacked on one another. Example:
the Sierra Nevada Mountains in North America