science 3 Flashcards
who first posed the theory of continental drift and when
Alfred Wegener
what is the theory of continental drift
a theory that all the continents were connected to each other and then drifted away
what is seafloor spreading
the formation of fresh areas of oceanic crust which occurs through the upwelling of magma at mid-ocean ridges and its subsequent outward movement on either side.
how old is the sea floor
the oldest seafloor rocks found were 200million years old
how do tectonic plates move
through currents on the mantle
from core outwards, name the different layers
the inner core, outer core lower mantle, upper mantle, crust, lithosphere
how thick is the crust
up to 75 km thick
name the types of crust
oceanic crust and continental crust
what is the oceanic crust
the crust found on the ocean floor
what is the continental crust
the crust that forms continents
which is denser oceanic crust or continental crust
oceanic crust because it contains less silicon and more iron and magnesium
which is thicker oceanic crust or continental crust
continental crust
what are the 3 types of tectonic plate movement at boundaries
diverging, converging, transform
what is a diverging tectonic plate movement
where plates are moving apart from each other. this often leads to magma rising from the gap, cooling, and creating new crust.
what is a converging tectonic plate movement
when 2 plates collide with each other. this creates volcanoes. these are also known as destructive boundaries.
what is a transform tectonic plate movement
is where two plates are sliding parallel to each other but in opposite directions. when this happens there is an earthquake.
what is magnetic striping
Magnetic Striping. Magma contains many materials which are magnetically affected. When this magma is ejected from the mantle and begins forming a new crust, these materials align to the earth’s magnetic field. The crust hardens, and the magnetic alignment is fixed (just as in normal magnets, made by using a similar process).
what has the old pre-continental drift land mass been named.
Pangaea
Pangaea gradually broke into two major landmasses: ____ in the north and ____ in the south.
Laurasia, Gondawa
what are explosive eruptions
subduction, generates heat, melting rock and forming magma. The magma rises up in huge packets through lines of weakness in the crust. It accumulates in spaces called magma chambers and is occasionally released to the surface as the pressure builds up.
What causes an earthquake
It is caused by the rapid release of energy as the tectonic plates move. friction between the plates must be overcome before they can move. when the force is great enough, the plates suddenly move as friction can no longer hold them.
how would one detect an earthquake
Earthquakes are measured using an instrument called a seismometer.
how did scientists find out about seafloor spreading
In 1872, scientists were surveying for an undersea cable, They did this by dropping down very long cables and measuring their length. they discovered a large mountain ridge in the middle of the Atlantic Ocean. The ridge was found to extend a long way in the South Atlantic, but the extent of the ridge was not investigated.
when did Alfred Wegner think of his theory of continental drift?
1912
what were the two premises of Alfred Wegener’s continental drift
that the continents fitted together like a jigsaw and that there were organisms spread across different continents that are known to not be able to travel that far.
why was Wegner’s theory widely disputed by scientists
because there was no known mechanism that would allow continents to move.
what are the 2 things that led to Hess’s theory
Flat-topped mountains in the south pacific and undersea mountains
how many large tectonic plates are there
7
how many medium tectonic plates are there
10
how many small tectonic plates are there
60
how are ocean currents affected by tectonic plates
crust splitting often leads to create new currents
how are flora and fauna affected by continental drift
the isolation of flora caught between the rift of continents leads to unique species of the previous plants.
what is a diverging plate movement known for doing
it is known for creating new crust through the release of magma.
what is a converging plate movement known for doing
it is known for making subductions that create volcanoes.
what is a transform plate movement known for doing
it is known for creating earthquakes.
why is the crust moving
because of sea floor spreading
