the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side.
What causes the magnetic fields?
Earth's outer core
What is reversed polarity?
It is after a magnetic reversal when a magnet points south
What is transform?
It is where plates slide past each other
What is divergent boundaries?
It is where two plates are moving away from each other and new crust is forming from magma that rises to the Earth's surface between the two plates.
Why does seafloor spreading occur?
It occurs because molten material beneath Earth's crust rises to the surface
What is seafloor spreading?
Seafloor spreading is the formation of new areas of oceanic crust, which occurs through the rising of magma at midocean ridges and its outward movement on either side.
What is the abyssal plain?
When sediment forms on top of the oldest oceanic crust, making smooth seafloor
How do you detect magnet fields on the seafloor?
by using a magnetometer
Where was the Himalayan mountain range of india formed?
convergent boundary
Scientists believe that differences in ____ cause hot, plasticlike rock in the asthenosphere to rise toward Earthh's surface.
density
What are two examples of tectonic activity?
earthquakes and volcanoes
Who is Alfred Wegener?
he is a German Scientist who studied whether Earth's continents move
Where does plates of the lithosphere float?
in the asthenosphere
What is a mid-ocean ridge?
it is large mountain ranges in the middle of the ocean
What is continental drift?
it is the hypothesis that suggests that continents are in constant motion on Earth's surface
What is normal polarity?
it is when a magnetic field causes a magnet to point north
What is magnetic reversal?
it is when a magnetic field reverses
What is convergent-collision?
it is where plates of equal density crash together
What is convergent-subduction boundaries?
it is where the dense plate sinks below the les dense plate
What does the magnetometer show?
it shows parallel magnetic strips on either side of a mid-ocean ridge
Where do plates usually form?
plate boundaries
What is ridge push?
plates are pushed away from each other at mid-ocean ridges
The presence of the same _________ on several continents supports the hypothesis of continental drift.
rocks and fossils
Continental drift states that continents have moved ______ to thier current location
slowly
Where is the youngest part of the ocean floor found?
near ocean ridges
What causes earthquakes?
when 2 plates that have equal density collide, slide past each other, or seperate in a plate boundary
What is slab pull?
when a plate sinks below another plate, it pulls on the rest of the plate
What form mountains?
when continental plates collide together
What causes volcanoes?
when dense plates sink below less dense plates
What is convection currents?
when materials move based on differences in thier temperatures and desnites. Heat rises and cold sinks
What is Pangaea?
when wegener proposed that all continents were once part of a single supercontinent
Scientists have observed that the continetns move apart or come together at speeds of a few centimeters per _______
year
How did scientists map the depth of the ocean floor?
They did it by using a device called an echo-sounder
What do these parallel magnetic strips show?
They show alternate normal polarity and reversed polarity, showing that each stripe was formed at the mid-ocean ridge and then moved away
What evidence did scientists use to support thier hypothesis?
They use similar fossils, plants and climate
The existence of coal beds in Antarctica indicated that the continents once had _______
a tropical, rainy climate
The crust and upper mantle makes up Earth's _______
lithosphere