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. When one of the rifts opens into the existing ocean, the rift system is flooded with seawater and becomes a new sea.
The oceanic trenches bordering the continents mark regions where the oldest oceanic crust is reabsorbed into the mantle through steeply inclined, earthquake-prone subduction zones. Seafloor spreading ends Sea floor spreading midocean ridges are subducted.
In this module students examine data from sediments on the ocean floor, determine whether the data support the theory of sea-floor spreading, and calculate the rate of spreading of the East Pacific Rise.
The magmatism at the ridge is considered to be "passive upswelling", which is caused by the plates being pulled apart under the weight of their own slabs. Older seafloor is therefore colder than new seafloor, and older oceanic basins deeper than new oceanic basins due to isostasy.
These areas are named triple junctions and can be found in several places across the world today. The Red Sea is an example of a new arm of the sea. Questions for thought What are the shallowest major features of the Atlantic and Pacific Oceans? A spreading center includes a seismically active plate boundary zone a few kilometers to tens of kilometers wide, a crustal accretion zone within the boundary zone where the ocean crust is youngest, and an instantaneous plate boundary - a line within the crustal accretion zone demarcating the two separating plates.
This zone consists of easily deformed rock and in some regions reaches a depth of km. This spreading creates a successively younger ocean floor, and the flow of material is thought to bring about the migration, or drifting apart, of the continents. The transform faults lie between two neighboring offset ridges.
About Deep Sea Hydrothermal Systems: Lemoyne Street, Chicago, IL ; phone These… Shortly after the conclusion of World War IIsonar -equipped vessels crisscrossed the oceans collecting ocean-depth profiles of the seafloor beneath them. Debate and search for mechanism[ edit ] At the Mid-Atlantic Ridge and in other areasmaterial from the upper mantle rises through the faults between oceanic plates to form new crust as the plates move away from each other, a phenomenon first observed as continental drift.
Why does the seafloor slope downward away from midocean ridges? The Science Teacher, v. The magnetic history of the earth is thus recorded in the spreading ocean floors as in a very slow magnetic tape recording, forming a continuous record of the movement of the ocean floors.
The pull of the deeply plunging lithosphere is one of the forces that may drive plate separation. Want to thank TFD for its existence?
The ridge crest and its associated transform faults are the locus of nearly all shallow earthquakes occurring in mid-ocean areas. BoxRochester, New York ; phone In detail, midocean ridges are made up of short offset segments. You can help by adding to it.
The purpose of this activity is to make a simple model that shows the evolution of oceanic crust through sea-floor spreading and subduction.Seafloor spreading: Seafloor spreading, theory that oceanic crust forms along submarine mountain zones and spreads out laterally away from them.
Seafloor spreading is one of the two major processes of plate tectonics, the other being subduction. Seafloor spreading is the continuous process of forming new igneous rock at midocean ridges by injection of magma that forms new seafloor.
seafloor spreading, theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges.
First proposed in the early s by the A. If sea-floor spreading operates, the youngest oceanic crust should be found at the ridges and progressively older crust should be found in moving away from the ridges towards the continents.
This is the case. The oldest known ocean floor is dated at about million years, indicating that older ocean floor has been destroyed through subduction.
62 rows · Seafloor spreading is a geologic process in which tectonic plates—large slabs of Earth's lithosphere—split apart from each other. sea-floor spreading The theory that the ocean floor is created at the spreading (accretionary) plate margins within the ocean basins.
Igneous rocks rise along conduits from the mantle, giving rise to volcanic activity in a .Download