Seafloor spreading occurs along mid ocean ridges large mountain ranges rising from the ocean floor.
A movement of thr sea floor along many rifts.
Plates are composed of lithosphere about 100 km thick that float on the ductile asthenosphere.
The east african rift was thought to be a failed arm that was opening more slowly than the other two arms but in 2005 the ethiopian afar geophysical lithospheric experiment reported that in the afar region september 2005 a 60 km fissure opened as wide as eight meters.
The mid atlantic ridge for instance separates the north american plate from the eurasian plate and the south american plate from the african plate the east pacific rise is a mid ocean ridge that runs through the eastern pacific ocean and separates the pacific plate from the north american.
The following features are shown at example depths to scale though each feature has a considerable range at which it may occur.
5 1 1 sea floor spreading and plate tectonics.
The scientists also observed that the crest of the ridges had a topography that closely resembled volcanic rift zones on land.
Continental shelf 300 feet continental slope 300 10 000 feet abyssal plain 10 000 feet abyssal hill 3 000 feet up from the abyssal plain seamount 6 000 feet.
The mid ocean ridge is the most extensive chain of mountains on earth stretching nearly 65 000 kilometers 40 390 miles and with more than 90 percent of the mountain range lying in the deep ocean.
This evidence led early marine geologists to deduce that the mid ocean ridges were formed by seafloor volcanoes.
As the lithospheric plates move across earth s surface driven by forces as yet not fully understood they interact along their boundaries diverging converging or slipping past each other.
Plate movement is possible because the lithosphere asthenosphere boundary is a zone of detachment.
The massive mid ocean ridge system is a continuous range of underwater volcanoes that wraps around.
The sea floor spreading hypothesis was first formulated by hess 1960 1962 the mid ocean ridges which are characterized by unusually high heat flow along their crests are the largest topographic features on the surface of the earth.
This graphic shows several ocean floor features on a scale from 0 35 000 feet below sea level.
Continental drift large scale horizontal movement of continents relative to one another and to the ocean basins during one or more episodes of geologic time.
By combining the sea floor spreading theory with continental drift and information on global seismicity the new theory of plate tectonics became a coherent theory to explain crustal movements.
At their crests they had v shaped central valleys with steep faults on either side.
The red sea is an example of a new arm of the sea.
