Why are continental shelves below sea level?

Some 18,000 years ago, at the peak of the most recent ice age, much of the Earth’s water was frozen into huge masses of ice called glaciers. The sea level dropped, exposing continental shelves.

Why height is measured from sea level?

Sea level is the base level for measuring elevation and depth on Earth. Because the ocean is one continuous body of water, its surface tends to seek the same level throughout the world. Sea level is measured in relation to the adjacent land. Just like the ocean, the elevation of land may rise and fall over time.

Is the continental shelf below sea level?

A continental shelf typically extends from the coast to depths of 100–200 metres (330–660 feet). It is gently inclined seaward at an average slope of about 0.1°. In nearly all instances, it ends at its seaward edge with an abrupt drop called the shelf break.

Why is most ocean life found on near the continental shelf?

These flat, shallow ledges gently slope from the shore to a steep drop called the continental slope. The shallow, sunlit waters of the continental shelf are flooded with nutrients, supporting an abundance of sea life. Many animals live here. Ninety percent of the world’s fish are found along the continental shelf.

Why are continents above sea level?

This increase is linked to the continental crusts rising above the oceans. As Earth’s land plates began to shift and move, less dense rock may have been forced upward, shaping the continents we see today on Earth’s crust.

How do changes in sea level affect the continental shelf?

Changes in sea level have profoundly affected the biodiversity and distribution of marine life on continental shelves. At the peak of the last ice age the area of shallow continental shelf, where benthic photosynthesis is possible, was approximately 80\% less than its present extent (Tassinari et al., 1996).

What is the height of the sea level?

The term APSL means Above Present Sea Level, comparing sea levels in the past with the level today. Earth’s radius at sea level is 6378.137 km (3963.191 mi) at the equator. It is 6356.752 km (3949.903 mi) at the poles and 6371.001 km (3958.756 mi) on average.

How is sea life on the continental shelf different from sea life in the deep ocean?

Continental shelves teem with life because of the sunlight available in shallow waters, in contrast to the biotic desert of the oceans’ abyssal plain. The pelagic (water column) environment of the continental shelf constitutes the neritic zone, and the benthic (sea floor) province of the shelf is the sublittoral zone.

Why does most of the ocean life live in or at least visit the ocean surface?

Organisms that photosynthesize depend on sunlight for food and so are restricted to the photic zone. Since tiny photosynthetic organisms, known as phytoplankton, supply nearly all of the energy and nutrients to the rest of the marine food web, most other marine organisms live in or at least visit the photic zone.

Why are continents above sea level quizlet?

Why do continents move? Why are continents above sea level? continental rocks are less-dense than oceanic rocks. What does Isostasy indicate about the interior structure of the Earth?

Why do the continents rise above the ocean quizlet?

-Lithosphere with continental crust always rides above the lithosphere with oceanic crust because oceanic crust is more dense and thicker. -Because it is where adjacent lithospheric plates spread apart from one another, and new lithosphere is produced.