The Earth’s crust is broken up into pieces called plates. The crust moves because of movements deep inside the earth. Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. The convection currents move the plates.

Convection currents form because a heated fluid expands, becoming less dense. The less-dense heated fluid rises away from the heat source. As it rises, it pulls cooler fluid down to replace it. This fluid in turn is heated, rises and pulls down more cool fluid.

When sun rays hit the land the land gets heated up. Then the air nearest to the land gets heated up too and it becomes lighter and rises up. The air from higher altitude which is cooler and thus heavier sinks down to fill the space left by warm air. This cycle repeats and convection currents are set up.

Convection currents are the result of differential heating. Lighter (less dense), warm material rises while heavier (more dense) cool material sinks. It is this movement that creates circulation patterns known as convection currents in the atmosphere, in water, and in the mantle of Earth.

Convection currents generated within the asthenosphere push magma upward through volcanic vents and spreading centres to create new crust. According to the theory of plate tectonics, the asthenosphere is the repository for older and denser parts of the lithosphere that are dragged downward in subduction zones.

Mantle convection causes tectonic plates to move around the Earth’s surface. It seems to have been much more active during the Hadean period, resulting in gravitational sorting of heavier molten iron, nickel, and sulphides to the core and lighter silicate minerals to the mantle.

Convection creates a dry atmosphere that caramelizes the sugars faster when roasting, so foods like meats and vegetables get browner, but the interiors stay moist. It saves energy: Because food cooks faster in a convection oven, and generally at a lower temperature, it’s a bit more energy efficient than a regular oven.

It has long been known that throughout the mantle there are convection currents circulating, caused by the difference in temperature at the earth’s interior and surface. Hot material from the earth’s outer core rises very slowly (over millions of years) throughout the mantle.

Convection currents within the mantle provide one potential driving force for plate movement. The plastic movement of the mantle material moves like the flow of mountain glaciers, carrying the lithospheric plates along as the convection movement in the mantle moves the asthenosphere.

When two oceanic plates converge, the denser plate will end up sinking below the less dense plate, leading to the formation of an oceanic subduction zone. Whenever a subduction zone is formed, the subducted plate will end up being partially melted by the earth’s internal magma and molten.

Continental and Oceanic Plates Continental plates typically do not subduct beneath oceanic plates because of how thick and buoyant they are. Instead, continental plates typically bend, break and crumple, creating folds, thick creases and mountain ranges like the Andes, Swiss Alps and the Himalayas.

What happens when two oceanic plates collide? When two oceanic plates collide, the denser plate is subducted and some material rises upward and forms an ISLAND. Ocean floor is pushed away from a midocean ridge to form new sea floor.

When two plates carrying continents collide, the continental crust buckles and rocks pile up, creating towering mountain ranges. When an ocean plate collides with another ocean plate or with a plate carrying continents, one plate will bend and slide under the other. This process is called subduction.

lithosphere

Subduction occurs when two plates collide at a convergent boundary, and one plate is driven beneath the other, back into the Earth’s interior. Not all convergence leads to subduction. Continental rocks are too buoyant to be forced downward, so when continents collide, they crumple but stay at the surface.

List the four major features of subduction zones….Terms in this set (30)

• Oceanic lithosphere goes under the oceanic plate.
• Scraped sediments accumulate on upper plates.
• Igneous and metamorphic rocks form mountainous topography.

Subduction zones are plate tectonic boundaries where two plates converge, and one plate is thrust beneath the other. Above and below this area on the fault, stress cannot build up, and the movement between the plates occurs relatively smoothly through time, and thus does not produce large earthquakes.

Why do so many earthquakes originate in this region? The belt exists along boundaries of tectonic plates, where plates of mostly oceanic crust are sinking (or subducting) beneath another plate. Earthquakes in these subduction zones are caused by slip between plates and rupture within plates.

In a megathrust earthquake area, one plate pushes under another in a so-called subduction zone. The fault interface is almost horizontal. Typically the fault descends at 10–20° from the horizontal. Together, these factors make a megathrust earthquake the most powerful in existence.

The Cascadia Subduction Zone (CSZ) is a 1,000 km (620 mi) long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino in northern California. It separates the Juan de Fuca and North America plates.

565 miles