Chapter 9 Plate Tectonics Flashcards
Asthenosphere
soft layer of rock in the mantle
Conduction
heat transfer by direct contact of particles of matter
Continental drift
the idea that continents slowly moved over Earths surface
Convection
heat transfer by the movement of a heated fluid
Convergent boundary
when two plates come together
Deep-ocean trench
an underwater canyon where subduction occurs
Divergent boundary
when two plates move apart from each other
Density
a measure of how much mass there is in a volume of a substance
Fault
breaks in Earths crust where rocks have slipped past each other
Fossil
persevered remains or any trace of an ancient organism preserved in rock
Lithosphere
the uppermost part of the mantle that is rigid
Mid-ocean ridge
a chain of underwater mountains along which sea floor spreading occurs
Pangaea
a super continent meaning “all the lands”
Plate tectonics
the geological theory that states that pieces of the Earths lithosphere are constant, slow motion, driven by convection currents in the mantle
Radiation
the transfer of energy through empty space
Rift valley
a deep valley on land that forms along a divergent valley
Sea-floor spreading
the process that continually adds new material to the ocean floor
Seismic waves
a wave produced by an earthquake
Sonar
a device that bounces sound waves off underwater objects and than records the echoes of these sound wave
Subduction
the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle
Transform Boundary
when two plates slip past each other moving in opposite directions
What is the evidence that was used to support the theory of continental drift?
land features-mountain ranges in Africa matches with a range in Argentina/coal field in Europe is also in North America
fossils-similar fossil are found on different continents
climate changes- scratches made in rocks from glaciers/fossils of tropical plants are found in polar climates
What is the layers of Earth from surface to center?
crust, mantle, outer core, inner core
(lithosphere, asthenosphere: two parts of the mantle)
What is the general composition/condition of each of Earth’s layers?
crust-Earth’s outer skin that is a solid layer of rock that includes both dry land and the ocean floor
mantle:
lithosphere-the uppermost part of the mantle that is rigid
asthenosphere-the lower part of the mantle
inner core-a dense ball of solid metal
outer core-a layer of molten metal
they vary in size, composition, temperature and pressure
What causes the movement of Earth’s tectonic plates?
convection currents
What generates Earth’s magnetic fields?
movements in the liquid outer core
What happens when a heat source is removed from a fluid?
the convection current stops
What is direct evidence of Earth’s interior?
rock samples
What is indirect evidence of Earth’s interior?
seismic waves
What is the relationship between pressure and depth?
proportional relationship-when one goes up the other goes up/one goes down the other goes down
What is the results of collisions between Earth’s tectonic plates?
oceanic and oceanic = subduction
oceanic and continental= oceanic plunges beneath the continental crust
continental and continental= collision head on
Where are Mid-ocean ridges found?
deep underwater
Where does sea-floor spreading occur?
Mid-Ocean ridges
Where does subduction occur?
where trenches are
Why is the old oceanic crust more dense than new oceanic crust?
the old oceanic crust has a longer time to cool making it denser
Why was Wegener’s theory originally rejected?
Wegener could not provide a satisfactory explanation for the force that pushes or pulls the continents
What three factors set convection currents in motion?
temperature difference, change in density, pull of gravity
What are the four steps within a convection current?
- heats 2. rises 3. cools 4. sinks
How many years ago did Pangaea exist?
300 million years ago
How manny years has it been since Pangaea began to break apart?
225 million years
Convection currents form in what part of Earth’s atmosphere?
troposphere
