Both horst and graben processes form mountains {orogeny}.
Mountain building processes can make large lowered masses {graben}|, as in Death Valley USA, Red-Sea basin, and East-Africa rift valleys.
Mountain building processes can make large raised masses {horst}|, as in Sierra Nevada Mountains and Alps Mountains.
Upper-mantle convection currents rise near surface at 20 locations {plume, mantle} {hot spot, mantle}|. Plumes have 300,000 meters diameter. Plumes in crustal-plate middle can send alkali-rich basalt lava up to surface to form volcanoes, as in Hawaiian Islands.
Colliding plates can move straight into each other {pressure ridge} to make mountains, with no overriding. Alternatively, one plate can slide over other one, forming both mountains and ocean trenches.
Along rift, lava makes mountain range {ridge, mountain}|, with valley down middle.
At plate sides opposite from rifts, plates slide under other plates {subduction, plate}|. Plates meet {subduction zone}, and one plate goes up and the other goes down, at 45-degree angles. Plates can go 700 kilometers into mantle. Subduction is at North-America and South-America west coasts, at Asia east coast, and from Spain and north Africa to Italy, to Greece, to Turkey, to India, to Burma, to Celebes.
Ocean crust and underlying mantle {ophiolite} can uplift onto continent.
Colliding plates can make especially deep and steep ocean floor {trench}|.
5-Earth Science-Planet-Plate Tectonics
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0225