Oceanic crust, extending 5-10 kilometers (3-6 kilometers) beneath the ocean floor, is mostly composed of
different types of basalts
. Geologists often refer to the rocks of the oceanic crust as “sima.” Sima stands for silicate and magnesium, the most abundant minerals in oceanic crust. (Basalts are a sima rocks.)
What kind of rock is the seafloor made of?
This bubbled-up magma is cooled by frigid seawater to form
igneous rock
. This rock (basalt) becomes a new part of Earth’s crust. Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor.
Which rock is the seafloor oceanic crust made of?
Oceanic crust is generally composed of dark-colored rocks called
basalt and gabbro
. It is thinner and denser than continental crust, which is made of light-colored rocks called andesite and granite.
Which rock is the seafloor oceanic crust made of quizlet?
Oceanic crust is made of
basalt lavas
that flow from the mantle onto the seafloor and harden into two types of igneous rock: basalt and gabbro (Figure below).
Which rock type are the oceanic crust and continental crust made?
Oceanic crust is largely made up of
basalt, diabase, gabbro and other volcanic rocks
. Continental crust is composed largely of granitic rocks that are of low-density.
Where is the oldest oceanic crust found?
The oldest patch of undisturbed oceanic crust on Earth may lie
deep beneath the eastern Mediterranean Sea
– and at about 340 million years old, it beats the previous record by more than 100 million years.
Where is oceanic crust found?
Oceanic crust, the outermost layer of Earth’s lithosphere that is found
under the oceans
and formed at spreading centres on oceanic ridges, which occur at divergent plate boundaries. Oceanic crust is about 6 km (4 miles) thick.
What rocks are found in the ocean?
- Gabbro. Gabbro is usually dark in color — black or gray — and is a coarse-grained igneous rock that makes up most of the seabed. …
- Basalt. …
- Serpentine. …
- Peridotite. …
- Olivine. …
- Volcanic Massive Sulfides.
Who discovered seafloor spreading?
Harry Hess
: One of the Discoverers of Seafloor Spreading.
How is new seafloor formed?
Seafloor spreading helps explain continental drift in the theory of plate tectonics. When oceanic plates diverge, tensional stress causes fractures to occur in the lithosphere. … At
a spreading center, basaltic magma rises up the fractures and cools on the ocean floor
to form new seabed.
What is Earth’s densest layer?
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.
What comes first crust or mantle?
Just below the crust lies the
mantle
. The mantle is semi-liquid, sort of like a malleable plastic and makes up 84% of Earth’s volume. Earth’s mantle is 2,900 km thick and is broken down into 3 main zones, the lithosphere, asthenosphere, and mesosphere.
Why is oceanic crust made of more mafic minerals?
Some mafic and ultramafic rocks are found on Earth’s surface. However, because
magnesium and iron are denser than silica
, mafic rocks are denser than silicic rocks and tend to sink below them. … These cooled mantle rocks stick to the underside of the oceanic crust, thickening it over time.
What are the similarities and differences between oceanic crust and continental crust?
Continental crust is low in density whereas oceanic crust has a higher density
. Continental crust is thicker, on the contrary, the oceanic crust is thinner. Continental crust floats on magma freely but oceanic crust floats on magma scarcely. Continental crust cannot recycle whereas oceanic crust can recycle it.
Which is thicker oceanic or continental crust?
Continental crust is typically 40 km (25 miles) thick, while
oceanic crust is much thinner
, averaging about 6 km (4 miles) in thickness. … The less-dense continental crust has greater buoyancy, causing it to float much higher in the mantle.
Where is oceanic crust the thickest?
The crust is thickest
under high mountains
and thinnest beneath the ocean.
