hydrogenous sediments hydrogenous sediments are those sediments that are derived from water how can that be we just went through a long list of information about lithogenous sediments coming from Land how can sediment come from water you may be familiar with one very common hydrogenous sediment table salt we'll see why in a bit I should clarify hydrogenous sediments are derived from things that are dissolved in water things such as manganese nodules or phosphates and carbonates or even evaporites as mentioned in a previous module sea water contains a lot of dissolved substances and many of the elements on the periodic table if conditions change these dissolved substances can actually precipitate out or change from the dissolved state to the solid state speaking in terms of volume hydrogenous sediments make up a very small portion of the total sediment in the ocean especially when you compare it to lithogenous sediments let's kick off with manganese nodules these are roundish lumps about 5 to 20 centimeters across that's not terribly large but is considerably larger than the small lithogenous sediments from earlier what's more impressive is that these nodules only grow about five millimeters per million years if you do the math on that it means that the five centimeter modules are about 10 million years old what happens is similar to a pearl being formed by an oyster while an oyster will form a pearl by depositing minerals around a grain of sand in the deep ocean some Central object like a rock or a shark tooth is covered in small layers of precipitated minerals over time these layers build up into the nodules that we see today why are these important these nodules have high concentrations of Manganese oxide and other valuable metals like Cobalt and copper metals that are used in our phones and computers today because of this there are efforts underway to mine these nodules from the seafloor but these efforts also come at a cost of the environment what's what's strange about these nodules is that they don't seem to make sense or rather their presence is odd if they grow that slowly why aren't they covered by other sediments this this ring-like structure can provide information about their growth so why does it appear that they grow in spurts can we recreate those spurts on land are there organisms involved in the production of these nodules that could explain why they don't get married but what organisms are they and why do they do it here's an image of a manganese nodule on the seafloor actually a bunch of nodules you can see that it's not just one or two of them lying around there are many of them there and cutting One open reveals that ring-like pattern similar to the trunk of a tree one of the major regions where nodule mining is beginning to be investigated is this Clarion clipperton Zone here in the North Pacific but it's not the only Zone where these things are found they can be found all over the world and many of them are outside of countries eezs or exclusive economic zones meaning that they can be mined by anyone but manganese nodules aren't the only hydrogenous sediment there are phosphates too but the ability of phosphate deposits on land means that humans aren't terribly interested in mining them from the ocean metal sulfides can be found near hydrothermal vents along the mid-ocean ridges carbonates can be found in areas with high biological productivity at the surface and evaporates can be more or less farmed in coastal regions evaporates are minerals that form when sea water evaporates this evaporation could be due to restricted circulation with the open ocean or in regions with excessively High evaporation our common table salt sodium chloride can be produced from seawater and what you see here is a large field where seawater pumped in allowed to evaporate and then the remaining salts scooped up and transported by truck to those processing plants that take care of the salt now once the salt has been completely scooped up the field is again flooded with seawater and the process repeats so the next time you put salt on your food remember that it's a hydrogenous sediment this is a very short blip on cosmogenous sediments going along with the word cosmoginis think Cosmos think Cosmic out of this world because that's exactly what cosmogenous sediment is it's sediment from extraterrestrial sources though the total proportion of cosmogenous sediment is somewhat insignificant relative to the other sediment types the amount of material deposited each day from space is kind of mind-boggling an estimate of 10 kilograms of cosmogenous material is deposited every second there are 2.2 pounds in a kilogram which means that over 40 pounds of sediment is deposited on Earth each second from extraterrestrial sources I know I did this earlier video but that number is just the picture you see here is an example of a cosmogenous particle it's distinguished by the extreme smoothness of its surface these particles called spherols are formed by impacts on Earth or other planets or from colliding asteroids the presence of these spherols is evidence that meteorites have crashed into Earth in the past we see here another shot of that KT boundary core the dark layer is debris produced from the impact of the meteorite and includes these glass-like globules called tektites that were produced from the intense heat of the impact because of their density they tended to settle out first followed followed by smaller finer particles