Explore the Deep Sea
Volcanoes & Vents
Introduction to plate tectonics and hydrothermal vents.
The Earth's structure is a bit like an egg:
- The "yolk" at its center is an iron core thousands of miles across.
- Around the core lies the mantle, a layer of super-hot rock thousands of miles thick.
- The outermost layer (the crust) varies in thickness from around 120 km (75 miles) under some continents to less than 3 km (2 miles) under some oceans. Like the broken shell of an egg, the Earth's crust consists of a set of interlocking plates. These tectonic plates are all moving slowly relative to each other.
On Earth, we see volcanoes in places where molten rock from the mantle rises through the crust to erupt at the surface. Most of these places are found in defined zones where the earth's crustal rocks have cracked because they are being pulled apart, pushed together or stretched as tectonic plates move.
Vents: ocean-floor geysers
We often see hot fluids surge out of the earth in areas of volcanic activity. When this happens on land, we call the erupting fluids "geysers" or "hot springs." Hot fluids shoot out of certain places on the seafloor, too. We call these places "hydrothermal vents" — vents for short. The emerging fluid is not only warm or hot, it often contains all sorts of dissolved minerals and sometimes precious metals. Many hydrothermal vents are found at mid-ocean ridges.