Geology Reference
In-Depth Information
Building mountains
Geologists call the process of mountain building orogenesis. Orogenic pro-
cesses are a result of plate movements and the various processes observed at the
different plate boundaries. Some mountains begin as volcanoes; others are the
result of crustal plates being stretched apart or crushed together.
Volcanoes and accretion
Volcanoes create mountains along the active continental margin of a subduction zone,
for example. At oceanic-oceanic convergent boundaries, mountain-building begins with
the creation of volcanoes along the seafloor.
As seafloor volcanoes build up, they form island mountains. Over time, with continuous
plate movements these volcanic mountains may be accreted or added to the continental
crust of another plate.
Accretion occurs when two plates converge and the crustal materials of the
subducting plate get piled up on top of the overlying plate. This process is illus-
trated in Figure 9-14. The accumulation of sediments, continental crustal rocks,
and some pieces of oceanic crust along the edge of the continent is called an ac-
cretionary wedge.
Figure 9-14: Accre-
tion of volcanic is-
lands onto contin-
ental crust.
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