rifts

A rift is an elongated region where the Earth's lithosphere is being stretched and thinned, causing fracturing, faulting, and subsidence. Rift zones occur in both continental and oceanic settings and are a key phase in plate tectonics where tectonic forces pull the crust apart.

In continental rifting, extension creates a rift valley bounded by normal faults. The crust thins and may host magmatic activity, forming volcanic highs and intrusions. If rifting continues, the continental crust can split to form a new ocean basin as sea floor spreading adds new crust at an adjacent ridge. Notable continental rift systems include the East African Rift, the Baikal Rift in Siberia, and the Rio Grande Rift in North America. These regions often feature fault-bounded blocks (horsts and grabens), volcanic fields, and sometimes large lakes.

In oceanic settings, rifting marks the early stage of seafloor spreading at mid-ocean ridges, where new oceanic crust forms as tectonic plates diverge. The Mid-Atlantic Ridge is the classic example, where magma wells up to create new crust and the ocean floor continuously widens.

Rifts are associated with seismic activity and can influence regional landscapes, climate, and biodiversity over millions of years. They provide important evidence for plate tectonics and the dynamic evolution of Earth's lithosphere, illustrating how continents can break apart and oceans can open.