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OCEAN BASINS Grade 8 Science 2012. OCEAN BASINS  Oceans form the largest ecosystem on Earth.  Much remains to be discovered about what lies below the.

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Presentation on theme: "OCEAN BASINS Grade 8 Science 2012. OCEAN BASINS  Oceans form the largest ecosystem on Earth.  Much remains to be discovered about what lies below the."— Presentation transcript:

1 OCEAN BASINS Grade 8 Science 2012

2 OCEAN BASINS  Oceans form the largest ecosystem on Earth.  Much remains to be discovered about what lies below the ocean’s surface.  Only about 1% of the ocean floor has been mapped  Most of the ocean (100 metres and below) is pitch-black.

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4  Continental Shelf – the gradual slope between the coastline and the edge of the ocean basin  Continental Slope – a steep drop dividing the continental slope and the ocean basin  Abyssal Plain – wide, open, flat plains that stretch out along the ocean basin  Oceanic Trench – narrow, deep, and steep sided canyons running along some ocean floors. Some of the deepest places on Earth 

5 A JOURNEY ON THE OCEAN FLOOR  The and formation of the ocean landscape are due mainly to the movements of Earth’s tectonic plates.  Features in the ocean basins are much bigger than on land.  There are mountain ranges taller than the Himalayas.  Steep valleys deeper than the Grand Canyon.  Plains wider than the Canadian Prairies.

6 CONTINENTAL SHELVES & SLOPES  Ocean basins do not begin at the coastline. They begin may km out at sea.  The area between the coast and the edge of the ocean basin is actually a submerged part of the continent, called the continental shelf.  Continental Slopes exist at the edge of the shelves and plunge at steep angles to the sea floor.

7 SEAMOUNTS  Large underwater mountain peaks called seamounts exist at the edges of mid- ocean ranges.  Seamounts are most often found in clusters and are most common in the Pacific Ocean.

8 TRENCHES  Along the sea floor are narrow, steep-sided canyons, called trenches.  They are formed where the edge of an ocean plate pushes against the edge of a continental plate. As the plates move together, the ocean plate is forced to bend steeply down beneath the heavier continental plate.

9 TRENCHES (CONT.)  The deepest trench, Marianas Trench, extends 11 km below sea level.  Nearly SEVEN times deeper than the Grand Canyon and deep enough to submerge an object as tall as Mount Everest.

10 ABYSSAL PLAINS  Between the high mountains and the deep trenches, the ocean floors are very flat.  These wide open features are called abyssal plains.  They are formed of thick deposits of sediment, up to 1 km deep in places.

11  As tectonic plates move apart or together, some oceans expand, while other shrink. Precise measurements show that the Atlantic Ocean is expanding, carrying North America and Europe farther part at a rate of 3 cm per year.

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13 MID-OCEAN RIDGES  Long undersea mountain chains called mid-ocean ridges run along the ocean floor  These ridges are the youngest areas of the sea floor and are still being formed by volcanic eruptions.  Molten lava flows from these ridges, quickly hardening into new plate material that pushes tectonic plates further apart.  Mid-ocean ridges are more than 1000 km wide and rise over m above the sea floor.

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15 MAPPING OUT THE OCEAN FLOOR  Please get a textbook and open to page 361.


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