2. Ocean Shapes Earth
Many of earth's materials and geochemical cycles originate in the ocean. Sedimentary rocks now exposed on land were formed in the ocean. Ocean life laid down the vast volume of siliceous and carbonate rocks as well. The land is the way it is because of the influence from the ocean. Sea level changes and force of waves, tectonic activity, and erosion influence the physical structure and land forms of the coast.
The surface of the Earth is in a constant state of change. The surface of the earth is separated into different plates that move over the molten upper portion of the mantle called the asthenosphere. Oceanic and continental plates diverge, converge, and interact at boundaries all over the planet.
The type of movement depends on the type of plate.
At divergent boundaries, the plates separate to form a narrow rift valley. Here, geysers release of water, magma, or molten rock to solidify and form new crust. It is at these boundaries that oceanic crust is created. For example, the mid-ocean range is the world's longest mountain range at 65,000 kilometers long. The Mid-Atlantic ridge can be observed as the ridge rises above sea levels in Iceland, where the North American and Eurasian plates diverge.
Convergent boundaries are were plates collide into each other. At these boundaries one, or both, of the plates' edge buckle under the other. This may create a mountain range or subducting, or a deep seafloor trench if both plate edges collapse. The Himalayas were formed 55 millions years ago when the Eurasian and Indo-Australian continental plates converged. The Marianas trench was created when the Pacific Plate subducted beneath the smaller Mariana Plate in the Pacific Ocean. All of these changes occurred on the ocean floor.
The movement of tectonic oceanic plates hugely impacts life on the land. As the dense oceanic tectonic plates slowly slide under lighter continental plates they reshape the ocean basins, continental shelves, inland seas, and the continents. When large earthquakes happen near the coast, the ocean can restructure the surface of coastal lands with shaking, sea level change, landslides, and tsunami wave force.
Erosion is another processes that demonstrates how the ocean has influenced the structure of the land. Erosion is the break down of material, caused by air flow or water movement. On the coastal line it is extremely common for rock formations to experience a break down from various forms of erosion. Wave pounding is where the energy of the waves breaks pieces of the rocks away. Abrasion occurs when waves launch material from the sea at the rocks. this is an effective and rapid form of shoreline erosion. Corrosion can also occur when rock is exposed for long periods of time to the carbonic acid in sea water. The coastline has been, and is still, being shaped by erosion from the ocean.
The geological movement in the ocean shapes and impacts the earth in many different ways. The land is not only influenced by the ocean, it is physically shaped and moved by it.
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