At first the driving force for spreading was argued to be convection currents in the mantle. Since then, it has been shown that the motion of the continents is linked to seafloor spreading by the theory of
plate tectonics
, which is driven by convection that includes the crust itself as well.
What force causes the continents to drift?
The theory of plate tectonics suggests that it is
convection currents in the
mantle of the earth that causes the movement of the continental plates.
What causes seafloor spreading and continental drift?
Seafloor spreading and other tectonic activity processes are the result of
mantle convection
. Mantle convection is the slow, churning motion of Earth’s mantle. … As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense.
What forces caused the continents to move?
The movement of these tectonic plates is likely caused by
convection currents in the molten rock in Earth’s mantle below the crust
. Earthquakes and volcanoes are the short-term results of this tectonic movement. The long-term result of plate tectonics is the movement of entire continents over millions of years (Fig.
What causes the seafloor to move?
The seafloor changes because
of the earth plates moving causing magma to
spew in the water. The magma is then pushed outward causing the seafloor to move and change.
What are the three types of seafloor spreading?
There are three types of plate-plate interactions based upon relative motion: convergent, where plates collide,
divergent
, where plates separate, and transform motion, where plates simply slide past each other.
What are the 4 evidence of continental drift?
The evidence for continental drift included
the fit of the continents; the distribution of ancient fossils, rocks, and mountain ranges; and the locations of ancient climatic zones
.
What caused Pangea to break up?
About 180 million years ago the supercontinent Pangea began to break up. Scientists believe that Pangea broke apart for the same reason that the plates are moving today. The movement is caused by
the convection currents that roll over in the upper zone of the mantle
.
Are continents floating?
The continents do not float on a sea of molten rock
. … Under the continents is a layer of solid rock known as the upper mantle or asthenosphere. Though solid, this layer is weak and ductile enough to slowly flow under heat convection, causing the tectonic plates to move.
Why did no one believe Wegener’s theory?
The main reason that Wegener’s hypothesis was not accepted was
because he suggested no mechanism for moving the continents
. He thought the force of Earth’s spin was sufficient to cause continents to move, but geologists knew that rocks are too strong for this to be true.
What do scientists now think is causing the continents to move?
Plate tectonic theory
explains why continents continue to move. The planet’s outer shell consists of plates that move a few centimeters a year. Heat from the Earth’s interior causes this motion to happen via convection currents in the mantle.
Where is Earth’s heat energy most concentrated?
Where Do We Find Geothermal Energy? Although heat from the center of the Earth is migrating to the surface everywhere, the heat is concentrated at
the edges of tectonic plates
.
What is the first step of seafloor spreading?
1.
A long crack in the oceanic crust forms at a mid ocean ridge
. 2. Molten material rises and erupts along the ridge.
What are the evidence of seafloor spreading?
Abundant evidence supports the major contentions of the seafloor-spreading theory. First, samples of the deep ocean floor show that
basaltic oceanic crust and overlying sediment become progressively younger as the mid-ocean ridge is approached
, and the sediment cover is thinner near the ridge.
Where is active seafloor spreading occurring today?
Where is active sea floor spreading occurring today? Seafloor spreading is the movement of old rock that is being pushed by the new young oceanic crust. This would be a divergent since the plates are separating from each other. Active seafloor spreading is occurring at
mid-ocean ridges
.
What are two pieces of evidence for seafloor spreading?
Several types of evidence from the oceans supported Hess’s theory of sea-floor spreading-
evidence from molten material, magnetic stripes, and drilling samples
. This evidence also led sci- entists to look again at Wegener’s theory of continental drift.
