What happens if the oceanic crust of the earth cracks

The thickness of the crust is critical to the subduction of plates, and therefore to the operation of plate tectonics. Basalts are less dense than mantle rocks, so a thicker oceanic crust makes plates more buoyant, and prevents their subduction into the mantle.

In the Archaean 2. As a result, the Earth was covered by a layer of basalt km thick, making subduction and therefore plate tectonics difficult — if not impossible.

Without plate tectonics, the rigid km outer shell of the Earth was immobile, and the surface of the Earth was flat, with no mountains or rift valleys. This explains the lack of volcanic rocks produced by partial melting of subducted basaltic crusts, as well as the absence of sediments coming from the erosion of granites that typically form above subduction zones.

Continental sediments and volcanic rocks produced by subducted basaltic crusts appear only about three billion years ago. So what initiated plate tectonics? Figuring out why this planet has a movable crust could tell geologists more not just about this planet, but about all planets or moons with solid surfaces, and whether they could have life, too. In , the film director James Cameron became the first person to dive solo all the way down the deepest gash on Earth.

He touched down 35, feet below the ocean surface in the Challenger Deep, a depression within the Mariana Trench, itself a much larger trough at the intersection of two tectonic plates.

Cameron collected samples throughout the trench, including evidence of life thriving on the seams of our planet. In a process called serpentinization, the water bubbles out of the plate and transforms the physical properties of the upper mantle.

This transformation allows methane and other compounds to percolate out of the mantle through hot springs on the otherwise frigid ocean floor. Similar processes on early Earth could have supplied the raw ingredients for metabolism, which may have given rise to the first replicating cells. It gives us an idea of what early life could have been on Earth. A microbial mat in white covers yellow corals near East Diamante volcano in the Pacific Ring of Fire.

The mat feeds off the chemical energy of hydrothermal vents. Pacific Ring of Fire Expedition. Recent research ties plate tectonic activity to the burst of evolution called the Cambrian explosion , million years ago, when a stunning array of new, complex life arose.

In December , researchers in Australia published a study of roughly drill cores from seafloor sites around the globe, some containing samples that were million years old. They measured phosphorus as well as trace elements like copper, zinc, selenium and cobalt — nutrients that are essential for all life.

When these nutrients are abundant in the oceans, they can spark rapid plankton growth. The researchers, led by Ross Large of the University of Tasmania, showed that these elements increased in concentration by an order of magnitude around to million years ago. Large and his team argue that plate tectonics drove this process. Mountains form when continental plates collide and shove rock skyward, where it can more readily be battered by rain.

Weathering then slowly leaches nutrients from the mountains into the oceans. Maybe more surprisingly, Large and his colleagues also found that these elements were low in abundance during more recent periods — and that these periods coincided with mass extinctions. These nutrient-poor periods happened when phosphorus and trace elements were being consumed by the Earth faster than they could be replenished, Large said.

Consider the case of carbon dioxide. A planet with too much carbon dioxide could end up like Venus, a planetary blast furnace. Plate activity on Earth has helped to regulate the level of carbon dioxide over the eons. The same weathering that pulls nutrients from mountaintops down into the oceans also helps to remove carbon dioxide from the atmosphere.

The first step of this process happens when atmospheric carbon dioxide combines with water to form carbonic acid — a compound that helps to dissolve rocks and accelerate the weathering process.

Rain brings both carbonic acid and calcium from dissolved rocks into the ocean. As the plates grind past each other, the jagged edges strike each other, catch, and stick, "locking" the plates in place for a time. Because the plates are locked together without moving, a lot of stress builds up at the fault line.

This stress is released in quick bursts when the plates suddenly slip into new positions. The sudden movement is what we feel as the shaking and trembling of an earthquake. The motion of the plates at a transform boundary has given this type of fault another name — a strike-slip fault.

The best-studied strike-slip fault is the San Andreas Fault in California. It is located at the boundary between the Pacific and North American plates and runs roughly miles 1, km through Northern and Southern California. The measurements clearly showed that two separate plates were converging.

More importantly, the thrusting observed on the French research cruise was about twice that found on the U. That proved that compression was more intense to the east -- confirming the Northwestern group's prediction on spreading rate and direction at the mid-ocean ridges.

Cochran says the research "gives insight into how strong and rigid plates are, how they respond to stress, and what their limits are before they break. It was basically an undergraduate's summer intern project. Media Contacts Cheryl L. Dybas, NSF, , email: cdybas nsf. The U. National Science Foundation propels the nation forward by advancing fundamental research in all fields of science and engineering.

NSF supports research and people by providing facilities, instruments and funding to support their ingenuity and sustain the U. Each year, NSF receives more than 40, competitive proposals and makes about 11, new awards. Those awards include support for cooperative research with industry, Arctic and Antarctic research and operations, and U.