Hydrothermal circulation

Hydrothermal circulation is the movement of hot water within the Earth. The word comes from ancient Greek, where "hydor" means water and "therme" means heat. This process happens mostly near places where the Earth is warm, such as areas with volcanic activity.

You can find hydrothermal circulation close to the surface or deep inside the Earth. It may occur where faults—the cracks in the Earth's surface—allow water to move, or where hot granite forms deep underground. It can also happen during major mountain-building events known as orogeny or when rocks change under heat and pressure, a process called metamorphism.

This movement of hot water is important because it can create valuable mineral deposits. Over time, these deposits can become sources of important materials like copper, gold, and other metals, which are used in many things we use every day. Hydrothermal circulation is a key part of shaping the Earth's surface and creating natural resources.

Seafloor hydrothermal circulation

Hydrothermal circulation in the oceans is the movement of water through mid-oceanic ridge systems. This includes both high-temperature vent waters near the ridge crests and much lower-temperature water flow through sediments and buried basalts farther from the crests. In both cases, cold seawater sinks into the seafloor, gets heated deep down, and then rises back up because it becomes less dense.

Hydrothermal vents are places on the seafloor where this hot water mixes with the ocean. The most famous of these are natural chimneys called black smokers. The heat for the high-temperature vents comes from newly formed basalt and, in the hottest vents, from an underlying magma chamber. The cooler vents are heated by older basalts that are still cooling. Studies show that these basalts can take millions of years to cool completely while supporting these water circulation systems.

Volcanic and magma related hydrothermal circulation

Hydrothermal circulation can happen anywhere there is a source of heat, like magma or volcanic vents, near groundwater. This can create interesting features such as hydrothermal explosions, geysers, and hot springs. Scientists study these systems closely, especially in areas where deep wells are used to harness geothermal energy.

Volcanic lakes are great places to observe these processes. Cold lake water seeps down, mixes with heated groundwater, and rises to form hot springs. These systems need a balance between cold water and geothermal heat to work properly, and they can create their own boundaries through processes like gas release and mineral buildup.

Deep crust

Hydrothermal circulation refers to the movement of water within the Earth's deep crust, moving from hot rocks to cooler areas. This process can be caused by the intrusion of magma, heat from radioactive rocks, heat from deep within the Earth, pressure from mountains like the Great Artesian Basin, and the release of water from certain types of rocks and sediments.

This circulation plays a key role in forming mineral deposits. Scientists have studied these deposits for many years. They classify them based on factors like temperature and pressure, and where the water comes from, such as magma or seawater. Examples include porphyry copper deposits and Mississippi Valley-type deposits.