Even on the ocean floor there are mountains! Let’s discuss each.
Continents
Continents are relatively old (billions of years) compared to the ocean basins (millions of
years). Because the continents have been around for billions of years, a lot has happened to
them! As continents move over the Earth’s surface, mountains are formed when continents
collide. Once a mountain has formed, it gradually wears down by weathering and erosion.
Every continent has mountain ranges with high elevations (Figure2.8). Some mountains
formed a very long time ago and others are still forming today:
- Young mountains(< 100 million years) – Mountains of the Western United States
(Rocky Mountains, Sierra Nevada, Cascades), Mountains around the edge of the Pa-
cific Ocean, Andes Mountains (South America), Alps (Europe), Himalayan Mountains
(Asia) - Oldmountains(>100millionyears)–AppalachianMountains(EasternUnitedStates),
Ural Mountains (Russia).
MountainscanbeformedwhentheEarth’scrustpushesup, astwocontinentscollide, likethe
Appalachian Mountains in the eastern United States and the Himalayas in Asia. Mountains
can also be formed by a long chain of volcanoes at the edge of a continent, like the Andes
Mountains in South America.
Figure 2.8: Features of continents include mountain ranges, plateaus, and plains. ( 27 )Over millions of years, mountains are worn down by rivers and streams to form high flat
areas calledplateausor lower lyingplains. Interior plains are in the middle of continents
while coastal plains are on the edge of a continent, where it meets the ocean.