The surface of the Earth is composed of a mosaic tectonic plates moving with respect to each other. The Earth is made of seven major plates and several smaller plates.
As the plates move, new sea floor can be created. The plates form three different kinds of boundaries: convergent, divergent, and transform. Convergent boundaries are also called collision boundaries because they are areas where two plates collide. At transform boundaries, the plates slide and grind past one another. The divergent boundaries are the areas where plates are moving apart from one another.
Where plates move apart, new crustal material is formed from molten magma from below the Earth's surface. That is, until they get subducted and recycled under less-dense oceanic or continental crust. Deep ocean drilling and radiometric dating in the late s gave an accurate stratigraphy and precise date of the ocean floor. From studying the oxygen isotopes of the shells of microfossils in these cores, scientists were able to begin studying the Earth's past climates in a study known as paleoclimatology.
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Share Flipboard Email. Brooks Mitchell. Science Expert. Brooks Mitchell is an earth science educator and geologist who is currently the Education Coordinator for the Space Science Institute in Boulder, Colorado.
And much sediment never gets to the ocean floor, but is trapped instead on continental slopes and shelves, or in huge river deltas. Over the years, some of these continental slopes can accumulate several kilometers of sediment, while others can even become part of mountain ranges in continental plate-to-plate collisions.
Neither erosion nor subduction are expected to be constant processes over millions of years, and they are simply not good clocks. Humphrey's strawman ocean floor does not prove the Earth is young.
Humphreys states that "An alternative creationist explanation [for the amount of sediment on the ocean floor] is that erosion from the waters of the Genesis flood running off the continents deposited the present amount of sediment within a short time about 5, years ago" Humphreys If this catastrophic event was the cause, one would expect the ocean bottom to be covered in a single kind of sediment.
However, the type of sediment on the ocean floor varies considerably and matches a uniformitarian model. According to Duxbury et al. Sediments that come from preexisting rocks are termed terrigenous sediments. They include the sand, rock fragments, wood chips, and anything else that enters the ocean from the land.
Rock powder may be suspended in the ocean for many years and eventually form clay on the ocean floor. Biogenous sediment is produced by marine organisms. This type of sediment includes siliceous ooze and calcareous ooze and is dependent upon the biomass and skeleton formation of organisms inhabiting the water.
According to Rachel James , "Diatom oozes generally predominate in deep waters at high latitudes and in areas of coastal upwelling, whereas radiolarian oozes are found at low latitudes. The belt of siliceous sediments round the Antarctic consists of diatom ooze, whereas that in the equatorial Pacific is of radiolarian ooze. This is not consistent with a global flood model because such an event would have caused the seabed's sediments to be intermixed. Hydrogenous sediment is created by chemical reactions in seawater to form minerals that accumulate as sediment.
Sediment created by objects from space, such as meteors, is called cosmogenous sediment Duxbury et al. The distribution of sediment is uneven because sediment derived from the continents stays mostly on the continental shelf, which is the area of shallower water around the continents and which is never subducted.
There is also a much higher amount of sediment accumulation adjacent to deserts, where the wind blows continental sediment into the ocean. Humphrey also fails to account for the amount of debris that does not accumulate on the ocean floor. In fact, according to Rachael James , only between one and ten percent of skeletal debris becomes sediment.
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