It is due to the process of subduction; oceanic crust tends to get colder and denser with age as it spreads off the mid-ocean ridges. It gets so dense, that it sinks in the upper mantle (subduction). As the continental crust is lighter than the oceanic crust, the continental crust cannot subduct.

Continental crust, the outermost layer of Earth’s lithosphere that makes up the planet’s continents and continental shelves and is formed near subduction zones at plate boundaries between continental and oceanic tectonic plates. …

Oceanic and Continental crusts are alike because they both shift and move and grow. They differ by there rock types. Oceanic crust is made up of dense basalt while continental crust is made up of less dense granite.

Oceanic crust is denser because it generally melts to a higher fraction than continental crust. When rocks melt to 20–30% like they do at mid-ocean ridges, the result is more dense than when rocks melt to form continental plates, which is typically 1–5%.

Oceanic crust is thinner and more dense than continental crust. This is because it has been compressed by the weight of the oceans it carries above it. It is also much younger than Continental crust, as it is usually less than 200 million years old.

In geology, a crust is the outermost layer of a planet. The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust.

An example of this is the Gakkel Ridge under the Arctic Ocean. Thicker than average crust is found above plumes as the mantle is hotter and hence it crosses the solidus and melts at a greater depth, creating more melt and a thicker crust. An example of this is Iceland which has crust of thickness ~20 km.

It creates the crust of the Earth we walk on, and the crust that lies at the ocean floor. Oceanic crust is the part of the Earth’s crust that makes up the seafloor. It’s thinner, denser, and simpler in structure than the continental crust.

The oceanic crust, on the basis of seismological studies of the seafloor, dredge hauls, drilling, and studies of ophiolites on land, is layered consisting of an upper sedimentary layer, a middle basaltic volcanic layer, and a lower third layer consisting of gabbroic plutonic rocks.

Oceanic crust is the part of Earth’s lithosphere that is under the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima. It is thinner than continental crust, or sial, generally less than 10 kilometers thick, however it is more dense, having a mean density of about 3.3 g/cm3.

The continental crust is also less dense than oceanic crust, although it is considerably thicker. As a consequence of the density difference, when active margins of continental crust meet oceanic crust in subduction zones, the oceanic crust is typically subducted back into the mantle.

At 25 to 70 km, continental crust is considerably thicker than oceanic crust, which has an average thickness of around 7–10 km. About 40% of Earth’s surface area and about 70% of the volume of the Earth’s crust is continental crust. Most continental crust is dry land above sea level.

Ocean-Continent Collisions When an oceanic and a continental plate collide, eventually the oceanic plate is subducted under the continental plate due to the high density of the oceanic plate. As time goes on the hot magma rising upward from the subduction zone causes further compression of the mountain belt.

When oceanic crust converges with continental crust, the denser oceanic plate plunges beneath the continental plate. This process, called subduction, occurs at the oceanic trenches. The subducting plate causes melting in the mantle above the plate. The magma rises and erupts, creating volcanoes.

Effects that are found at a divergent boundary between oceanic plates include: a submarine mountain range such as the Mid-Atlantic Ridge; volcanic activity in the form of fissure eruptions; shallow earthquake activity; creation of new seafloor and a widening ocean basin.

oceanic crust

Oceanic-Oceanic Plate Divergence is the divergence of plate boundaries of oceanic plates. When the oceanic plates move away from each other,magma rises from the mantle to cools and solidifies to form new sea floor, this is called sea-floor spreading.

The oldest parts of the oceanic crust are found farest from the mid ocean ridges at subduction zones and continental shelves.

Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth’s tectonic plates spread apart. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.