Plate tectonics, continental drift, spreading centers, subduction zones
Where oceanic crust meets continental crust. The denser oceanic plate is subducted, often forming a mountain range on the continent. The Andes is an example. According to the theory of Plate Tectonics, Earth's surface is made up of thin, rigid plates composed of oceanic crust, continental crust, or, in transitional areas. When two oceanic plates collide, it's more of a toss-up as to which plate will be forced Older oceanic crust is denser, so it would be more likely to subduct under a What is the difference between continental-continental and.
Tectonics Tectonic Plates, fossil correlations in Pangea and notional diagram of plate motions Plate tectonics is a scientific theory describing how continents move around on the mantle and how sea floor is produced and destroyed. Plate tectonics is able to account for many major geological features: What we know as solid ground rocks, soil, etc is the top of the Earth's continental crust.
For the most part, the crust is composed of old rocks whose density is relatively low, causing them to float on the much denser mantle.
Interactives . Dynamic Earth . Slip, Slide, & Collide
The solid crust and upper mantle are together a more-or-less rigid body called the lithosphere. The lithosphere is composed of approximately fourteen tectonic plateswhose thickness varies between about 25 and 65 km.
The crust under mountains is thicker than it is under low plains, much in the way that tall icebergs extend deeper underwater than short ones do. Oceanic crust is much thinner, being about 5 km thick, and is denser than continental crust. Why they do this is not well understood. It is almost certainly more complicated than just simple convection, as indicated by many illustrations, including the upper right hand one on this page.
Two main tectonic structures are spreading centers and subduction zones.
Difference Between Continental & Oceanic Plates | Sciencing
Spreading centers occur at the boundary between two plates that are moving apart, called divergent plate boundaries. Here the plate motion opens a gap between the plates and magma from the mantle rises up through it. When the magma reaches water at the ocean floor most spreading centers are in the oceanit cools and hardens, and becomes new oceanic crust.
As the plates continue to move apart, more and more new basaltic crust is created. The most famous spreading center is the Mid-Atlantic Ridgebut there are many others.
The crust continues to be forced deeper into the earth, where high heat and pressure cause trapped water and other gasses to be released from it.
Slip, Slide, & Collide
This, in turn, makes the base of the crust melt, forming magma. The magma formed at a subduction zone rises up toward the earth's surface and builds up in magma chambers, where it feeds and creates volcanoes on the overriding plate. When this magma finds its way to the surface through a vent in the crust, the volcano erupts, expelling lava and ash.
An example of this is the band of active volcanoes that encircle the Pacific Ocean, often referred to as the Ring of Fire.
Tectonic Plates and Plate Boundaries
Illustration depicting how island arcs are formed. A subduction zone is also generated when two oceanic plates collide — the older plate is forced under the younger one — and it leads to the formation of chains of volcanic islands known as island arcs.
Since the collision and subduction of plates is not a smooth process, large, powerful earthquakes are another phenomenon that result from this type of interaction.
Earthquakes generated in a subduction zone can also give rise to tsunamis.
A tsunami is a huge ocean wave caused by a sudden shift on the ocean floor, such as an undersea earthquake. If the wave reaches land, it can cause incredible destruction, like the Asian Tsunami, which killed more thanpeople in 11 countries across the Indian Ocean region in December Collision Zones and Mountains What happens when two continental plates collide?