Table of Contents
- 1 Which type of rock is subducted?
- 2 Which is much denser basalt or granite?
- 3 What happens when two oceanic plates collide?
- 4 Which type of crust is usually the oldest?
- 5 Is basalt a hard rock?
- 6 Which crust is thicker continental or oceanic?
- 7 What happens to the materials on top of a subduction plate?
- 8 What happens to the Earth’s crust during subduction?
Which type of rock is subducted?
Subduction zone has distinct metamorphic rocks: formation of jadeite and glaucophane of blueschist faceis. Metamorphism in subduction zone is related to dewatering processes in magma generation. Dewatering and higher pressure and temperature induce prograde metamorphism.
Which type of crust rock is more dense?
The more dense oceanic crust is below the continental crust and forms ocean basins. Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic rocks of the oceanic crust.
Which is much denser basalt or granite?
The crust of Earth is divided into two types: oceanic and continental. Most oceanic crust is composed of the rock basalt. Mafic rocks contain denser minerals and therefore, oceanic crust is denser than continental crust (the average density of basalt is 3.0 g/cm3 and granite is 2.7 g/cm3).
What type of rock is most dense oceanic or continental?
Continental crust is also less dense than oceanic crust, whose density is about 2.9 g/cm3. At 25 to 70 km, continental crust is considerably thicker than oceanic crust, which has an average thickness of around 7–10 km.
What happens when two oceanic plates collide?
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. Earthquakes generated in a subduction zone can also give rise to tsunamis.
What is the Protolith of Migmatite?
Migmatite is a composite rock found in medium and high-grade metamorphic environments. If present, a mesosome, intermediate in color between a leucosome and melanosome, forms a more or less unmodified remnant of the metamorphic parent rock paleosome.
Which type of crust is usually the oldest?
Cratons are the oldest and most stable part of the continental lithosphere. These parts of the continental crust are usually found deep in the interior of most continents.
What is the most dense layer of the Earth?
The densest layer (inner core) is at the center and the least dense layer (crust) is the outermost layer. The atmosphere, composed of gases, can technically be considered a layer as well and is obviously lighter than the crust.
Is basalt a hard rock?
Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt’s low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move >20 km from a vent.
What type of crust is usually the oldest?
Cratons are the oldest and most stable part of the continental lithosphere. These parts of the continental crust are usually found deep in the interior of most continents. Cratons are divided into two categories.
Which crust is thicker continental or oceanic?
Continental crust is typically 40 km (25 miles) thick, while oceanic crust is much thinner, averaging about 6 km (4 miles) in thickness.
Which is the deepest subduction zone in the world?
This explains why there are often zones of stretching, or crustal extension, in the upper plate at subduction zones. Where the subducting slab bends downward, a deep-sea trench forms. The deepest of these is the Mariana Trench, at over 36,000 feet below sea level.
What happens to the materials on top of a subduction plate?
Once subduction begins, the materials on top of the slab—sediments, water, and delicate minerals—are carried down with it. The water, thick with dissolved minerals, rises into the upper plate. There, this chemically active fluid enters an energetic cycle of volcanism and tectonic activity.
Where does the oceanic lithosphere go during subduction?
Subduction zones are where the cold oceanic lithosphere sinks back into the mantle and is recycled. They are found at convergent plate boundaries, where the oceanic lithosphere of one plate converges with the less dense lithosphere of another plate. The heavier oceanic lithosphere is overridden by the leading edge of the other plate.
What happens to the Earth’s crust during subduction?
General description. At that point, the density of the oceanic crust increases and provides additional negative buoyancy (downwards force). It is at subduction zones that Earth’s lithosphere, oceanic crust and continental crust, sedimentary layers and some trapped water are recycled into the deep mantle.