Why does the continental crust rise higher than the oceanic crust?

The less-dense continental crust has greater buoyancy, causing it to float much higher in the mantle. Its average elevation above sea level is 840 metres (2,750 feet), while the average depth of oceanic crust is 3,790 metres (12,400 feet). This density difference creates two principal levels of Earth’s surface.

Why is the oceanic crust lower than the continental crust?

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).

Why is continental crust higher than oceanic crust quizlet?

Areas of continental crust stand higher than areas of oceanic crust, because continental crust is THICKER and LESS DENSE than oceanic crust. The deepest parts of the ocean are near the continents, and out in the middle of the ocean, the water is relatively shallow.

Why does continental crust form more elevated land surfaces and is thicker in comparison to the lower lying and thinner oceanic crust?

The low density of continental crust causes it to “float” high atop the viscous mantle, forming dry land. Conversely, dense oceanic crust does not “float” as high—forming lower-lying ocean basins.

Why continental and oceanic crusts differ in their density?

Because continental crust is less dense than oceanic crust it floats higher on the mantle, just like a piece of Styrofoam floats higher on water than a piece of wood does. The mantle, oceanic crust and continental crust have different densities because they are made of different kinds of rock with different densities.

Is continental crust more or less dense than oceanic crust?

Continental crust is broadly granitic in composition and, with a density of about 2.7 grams per cubic cm, is somewhat lighter than oceanic crust, which is basaltic (i.e., richer in iron and magnesium than granite) in composition and has a density of about 2.9 to 3 grams per cubic cm.

Is continental crust thicker than oceanic?

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.

Is continental crust younger than oceanic?

Continental crust is almost always much older than oceanic crust. Because continental crust is rarely destroyed and recycled in the process of subduction, some sections of continental crust are nearly as old as the Earth itself.

What the difference between the continental and oceanic crust?

1. The oceanic crust is made up of basalt while the continental crust is made up of granite. 2. The oceanic crust is thinner while the continental crust is much thicker.

What is the difference between continental and oceanic crust quizlet?

The oceanic crust is thinner and denser, and is similar in composition to basalt (Si, O, Ca, Mg, and Fe). The continental crust is thicker and less dense, and is similar to granite in composition (Si, O, Al, K, and Na). The mantle is made of magnesium, iron and silicon.

Why are the continents above the ocean floor?

While the ocean basins lie much lower than sea level, the continents stand high—about 1 km (0.6 mile) above sea level. The physical explanation for this condition is that the continental crust is light and thick while the oceanic crust is dense and thin.

Where is continental rise found?

The continental rise is a low-relief zone of accumulated sediments that lies between the continental slope and the abyssal plain. It is a major part of the continental margin, covering around 10% of the ocean floor.

Does the ocean go under continents?

The ocean plates continue down underneath the continental plate until it reaches magma hot enough to melt it. It then becomes magma itself, as part of the mantel, and continues to circulate underneath the continental plate.

Would there be more ocean floor between the continents or less?

Wegener also noted differences between the continents and the ocean floor. He said the oceans were more than just low places that had filled with water. Even if the water was removed, he said, a person would still see differences between the continents and the ocean floor.

Does oceanic crust have the same composition as continental crust?

Oceanic crust formed at spreading ridges is relatively homogeneous in thickness and composition compared to continental crust. On average, oceanic crust is 6–7 km thick and basaltic in composition as compared to the continental crust which averages 35–40 km thick and has a roughly andesitic composition.

What formed continents and ocean floor?

The continents are made of a granite-like rock. Granite is made when hot, liquid rock cools and hardens under the Earth’s surface. The ocean floor is basalt rock, a mixture of silicon and magnesium. Mister Wegener said the lighter continental rock floated up through the heavier basalt rock of the ocean floor.

What is the order of ocean floor features between the shore of a continent and the deep ocean floor?

The shelf usually ends at a point of increasing slope (called the shelf break). The sea floor below the break is the continental slope. Below the slope is the continental rise, which finally merges into the deep ocean floor, the abyssal plain. The continental shelf and the slope are part of the continental margin.

What are the major parts of the ocean floor and how do they differ from each other?

Features of the ocean include the continental shelf, slope, and rise. The ocean floor is called the abyssal plain. Below the ocean floor, there are a few small deeper areas called ocean trenches. Features rising up from the ocean floor include seamounts, volcanic islands and the mid-oceanic ridges and rises.

What first accurately mapped the ocean floor?

The publication of Heezen and Tharp’s Physiographic Map of the North Atlantic in 1957 was the first map of the sea floor that enabled the general public to begin to visualize what the ocean floor really looked like.

Where does sea floor spreading happen on the ocean floor?

Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor. The Mid-Atlantic Ridge, for instance, separates the North American plate from the Eurasian plate, and the South American plate from the African plate.

How is new ocean floor and oceanic crust formed?

This process occurs when oceanic crust is pushed back into the mantle at subduction zones. As old oceanic crust is subducted and melted into magma, new oceanic crust in the form of igneous rock is formed at mid-ocean ridges and volcanic hotspots.

Which of the following increases with distance from a mid-ocean ridge?

The seafloor depth increases with distance away from the midocean ridges. The midocean ridges lie about 2.5 km below sea level.

What is the difference between continental drift and seafloor spreading?

How does seafloor spreading contradicts the continental drift theory? Similar to Wegener’s theory that continents do in fact move, Hess’ seafloor spreading contradicted Wegener’s continental drift in that it involved the ocean sea floor moving as it expanded—instead of continents ploughing through the sea.

What is the major difference between continental drift and plate tectonics?

The main difference between plate tectonics and continental drift is that plate tectonics describes the features and movement of Earth’s surface in the present and in the past whereas continental drift describes the drifting of Earth’s continents on the ocean bed.

What is the difference between continental drift and sea floor spreading quizlet?

The theory of plate tectonics states that the earth’s crust is rigid and the upper mantle is broken into slabs called plates. Continental drift is a hypothesis that suggests that earth’s continents move over time. Seafloor spreading is a theory that states that new ocean crust forms along mid-ocean ridges.