Where is sediment thickest on the ocean floor

Figure Cosmogenous sediments could potentially end up in any part of the ocean, but they accumulate in such small abundances that they are overwhelmed by other sediment types and thus are not dominant in any location. Similarly, hydrogenous sediments can have high concentrations in specific locations, but these regions are very small on a global scale. So we will mostly ignore cosmogenous and hydrogenous sediments in the discussion of global sediment patterns.

Much of this sediment remains on or near the shelf, while turbidity currents can transport material down the continental slope to the deep ocean floor. Lithogenous sediment is also common at the poles where thick ice cover can limit primary production , and glacial breakup deposits sediments along the ice edge.

Coarse lithogenous sediments are less common in the central ocean, as these areas are too far from the sources for these sediments to accumulate. Very small clay particles are the exception, and as described below, they can accumulate in areas that other lithogenous sediment will not reach.

The distribution of biogenous sediments depends on their rates of production, dissolution, and dilution by other sediments. We learned in section 7. So coastal areas remain dominated by lithogenous sediment, and biogenous sediments will be more abundant in pelagic environments where there is little lithogenous input.

In order for biogenous sediments to accumulate their rate of production must be greater than the rate at which the tests dissolve. Silica is undersaturated throughout the ocean and will dissolve in seawater, but it dissolves more readily in warmer water and lower pressures; in other words, it dissolves faster near the surface than in deep water.

Silica sediments will therefore only accumulate in cooler regions of high productivity where they accumulate faster than they dissolve.

This includes upwelling regions near the equator and at high latitudes where there are abundant nutrients and cooler water. Oozes formed near the equatorial regions are usually dominated by radiolarians , while diatoms are more common in the polar oozes.

Once the silica tests have settled on the bottom and are covered by subsequent layers, they are no longer subject to dissolution and the sediment will accumulate. Biogenous calcium carbonate sediments also require production to exceed dissolution for sediments to accumulate, but the processes involved are a little different than for silica.

Tiny fragments of this material plus other organic matter from marine plants and animals accumulate in terrigenous sediments, especially within a few hundred kilometres of shore. As the sediments pile up, the deeper parts start to warm up from geothermal heat , and bacteria get to work breaking down the contained organic matter. Because this is happening in the absence of oxygen a. Methane released by the bacteria slowly bubbles upward through the sediment toward the sea floor.

Within a few metres to hundreds of metres of the sea floor, the temperature is low enough for methane hydrate to be stable and hydrates accumulate within the sediment Figure Methane hydrate is flammable because when it is heated, the methane is released as a gas Figure The methane within sea-floor sediments represents an enormous reservoir of fossil fuel energy.

Although energy corporations and governments are anxious to develop ways to produce and sell this methane, anyone that understands the climate-change implications of its extraction and use can see that this would be folly.

Skip to content Chapter 18 Geology of the Oceans. Exercise Sediment thickness is often, for instance, related to chlorophyll patterns in the larger ocean because phytoplankton contributes a significant amount of sediment.

Shultz, D. Published on 10 May The authors. Any reuse without express permission from the copyright owner is prohibited. In future decades it will be interesting to see the contributions humans make to this in the form of discarded plastic materials and other forms of trash. The article claimed about 2 km.