Resource: Natural Wonders

Glaciated valleys
Throughout northern Europe, Canada, and North America, glaciers have played an important role in shaping the landscape. In mountainous regions subject to glaciation, the erosive force of glacial movement widens and deepens the V-shaped river valleys that guide the flow of the glaciers. When the ice thaws, a U-shaped valley is revealed. The transformed landscape is often marked with stray boulders known as glacial erratics, which have been deposited far from their source, and deep grooves, or striations, in exposed bedrock.

Petrified forests
The vibrant colors and preserved state of the logs and stumps suggest that a forest stood only yesterday. But it was millions of years ago that these trees were petrified, or converted into stone, through a series of natural processes. During this petrification, silica-rich groundwater filled decaying plant tissue with mineral particles. Scientists believe the silica came either from sand from an advancing desert, or from volcanic ash that buried the forest for thousands of years.

Mineral hot springs deposits
Geothermal features, including hot springs, geysers, and mud pots, appear at places on Earth's surface that are heated by underground magma chambers. Because minerals dissolve more readily in hot water than cold, hot springs often contain high mineral concentrations. When groundwater reaches the surface and cools, some of these minerals may be deposited out of solution. Stepped terraces, like those at Yellowstone's Mammoth Springs, are made of travertine, a mineral deposit that is usually white when deposited, but may be red, brown, or yellow if iron compounds or other minerals are present.

Salt lakes
The shores of the Dead Sea, bordered by Jordan and Israel, mark the world's lowest surface elevation: more than 400 meters (1,300 feet) below sea level. Mountain-fed rivers and streams transport the dissolved mineral salts for which this large landlocked lake is known. While most inland bodies of water have outlets that lead to the sea, no rivers drain the Dead Sea, so the salt accumulates. Because it is typically very hot there, water evaporates quickly and in great volume, enhancing the salt concentration. This makes it possible for visitors to float effortlessly in the Dead Sea.

Majestic waterfalls
Most waterfalls form over many years along streambeds composed of layers of hard, erosion-resistant rock and soft, easily eroded rock. Water gradually erodes the soft rock it passes over, leaving the more resistant rock. Where breaks in elevation occur along the residual hard rock formation, water may either gently cascade down a series of rock steps or plunge vertically to a pool below.

To view images of landscapes dramatically changed by erosion and weathering, check out Erosion and Weathering.

To learn more about glaciers, check out Glaciers and Mountain of Ice: If the Ice Melts.

To learn more about geothermal features, check out A Visit to Yellowstone.

• What natural processes do you see represented in this collection of images?
• For each of the natural wonders in the resource, explain how it was formed and its effects on the surrounding environment.
• What do these natural wonders have in common with each other?
• What natural wonders occur near where you live?