Marks the edge of the continental shelf. Is a steeper drop to the ocean floor, between 50 and 250.
Submarine canyons: Formed by erosion at least in part by turbidity currents . They form when sediments are disturbed by volcanic or earthquake activity. The muddy sediment that is now mixed in the water flows down the continental shelf and slope.
form along mid-ocean ridges. The water here is mineral rich; the hot newly formed crust comes in contact with cold ocean water causing minerals like sulfur, iron, copper, and zinc precipitate out and are deposited.
Manganese nodules – made also of iron and other metals, they form around grains of sand and are scatter across large areas of the deep ocean floor.
Calcium carbonates – form by precipitation directly from ocean water in warm climates. If this sediment is buried it can form limestone.
Evaporites – form where evaporation rates are high and ocean circulation is restricted. As water evaporates the remaining water becomes saturated with dissolved minerals which begin to precipitate. These sediments are generally called “salts.” Three common minerals that form this way are halite, gypsum, and calcium sulfate .
Oil and natural gas – ancient remains of microscopic organisms that were buried before they could decompose. Exposed to pressure of overlying rocks and the Earth’s internal heat the remains were transformed into oil and natural gas.
Major offshore reserves: Persian Gulf, Gulf of Mexico, off southern California, North Sea, and the East Indies.
Possible new reserves may be off the coast of Alaska and the Canadian Arctic, Asian seas, Africa, and Brazil
Gas hydrates – occurs as methane hydrate or methane.
Gas Hydrate is an ice-like crystalline solid formed from a mixture of water and natural gas, usually methane. They occur in the pore spaces of sediments, and may form cements, nodes or layers.
These occur beneath permafrost areas on land and under the ocean floor at depths below 525 meters. Most oceanic gas hydrates are created when bacteria break down organic matter trapped in ocean floor sediments. Other gases include ethane and propane.
Chunks of gas hydrates look like metals and evaporate quickly when exposed to warm temperatures and less pressure.
An estimated 20 quadrillion cubic meters of methane are locked in sediments. This is double the Earth’s coal, oil, and natural gas reserves combined.