Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents. Hydrothermal breccias are usually formed by hydrofracturing of rocks by highly pressured hydrothermal fluids. Tremor is commonly associated with the underground movement of magmatic or hydrothermal fluids. This is the remains of seafloor hydrothermal vents. Zeolites transform to other minerals under weathering, hydrothermal alteration or metamorphic conditions. The same phenomenon occurs near oceanic ridges in a formation known as hydrothermal vents. Some species have colonized abyssal depths near hydrothermal vents. Molybdenite occurs in high temperature hydrothermal ore deposits. Vermiculite forms by the weathering or hydrothermal alteration of biotite or phlogopite. Symbiotic bacteria can live near hydrothermal vents. These communities receive much less attention than the chemosynthetic communities associated with hydrothermal vents. Carbon dioxide is also introduced into the oceans through hydrothermal vents. It may occur as a vein deposit formed through hydrothermal activity particularly in limestones. Changes in composition can be caused by processes such as weathering or metasomatism (hydrothermal alteration). The term "hydrothermal" is of geologic origin.