Download Mountains Wear Down

Mountains, Rocks, and Sediment
At the same time that some processes push mountains up, other
processes wear them down. At Earth’s surface, water and wind break
rocks apart and move the pieces away. As long as mountains are
pushed up faster than they wear down, they grow taller. For this
reason, young mountains tend to be tall and steep. But eventually
mountain-building processes slow, then end. Water and wind take
over. Given enough time, all mountains become rounded hills, and
then they are gone. Countless mountains have formed and worn away
throughout Earth’s long history.
Rocks break down into loose pieces that can be carried by water
or wind. These pieces are called sediments. For example, sand on a
beach is sediment. Thick layers of sediments can build up in low-lying
areas, such as valleys, lakes, or the ocean. Pieces of sediments form
sedimentary rock as they are pressed together or joined by natural
cement.
The land becomes flatter as mountains wear down and valleys fill
with sediments. If tectonic plates were to stop moving, eventually the
surfaces of all the continents would be completely flat.
Mountains Wear Down
Mountains wear down as water and wind break their
rocks into sediments and carry them away.
Young Mountains
Most young mountains are
rugged. But even as they form,
their rocks are being broken
apart.
Old Mountains
How do mountains wear away?
Most old mountains are rounded.
Lower areas around them contain thick layers of sediments.
Chapter 8: Mountains and Volcanoes 255