Clean Water: Water on Earth [d]

S C U L P T I N G T H E E A R T H

"... every time the drop revisits the land, the land is different. Because other drops have changed it."
Hooper and Coady, 1998 - The Drop in My Drink

Running water sculpts the land. On planets with no running water, shifting rock and meteorite impacts shape the surface The moon is such a place. The footprints of astronauts may last there for millions of years.

Fig. Left: Footprints left by Apollo x astronauts in the Sea of Tranquility, 19xx. Right: Craters on the surface of the moon, a mix of impact and volcanic origin. Photos courtesy NASA.

On planets with water, running water quickly sculpts their surfaces. Footprints disappear in minutes on a beach. Grand structures crumble and dissolve. Even the scars of killer asteroid impacts are nearly erased from detection.

Fig. Eroding and overgrown temple of Angkor Wat in Cambodia.

The energy used to lift water into clouds reappears with a vengeance to move the earth. Energy transferred to flowing waters like the Colorado cuts the Grand Canyon. How many bulldozers and how much fuel would be required carve the Grand Canyon? Whatever that amount, rivers have the energy to spend. Energy flows with water according to the water cycle, originating from the Sun.

Weak acids dissolved in freshwater corrode the Earth's surface. Freshwater percolates through the ground and leaches minerals from soils. In arid environments it can leave a calcite-rich hardpan. In humid areas it can leave soils deprived of essential nutrients for plants.

Slowly but surely, aqueous chemical corrosion eats away at limestone monuments like the Sphinx.

On the flip side, water reshapes the land and brings renewal. If the moon were a construction site, the scars would never heal. On the Earth, even devastated landscapes renew themselves. Water reshapes the landscape and allows life to redecorate.

In some places, water creates an array of landscapes that are so universally beautiful, that we choose to preserve them.

Fig. Slide show. Click to access and enlarge.

The new shape of the land changes the environment and allows new possibilities for life. Before the Grand Canyon formed, the land was flat. Today the deep canyon exposes over a mile of rock. It snows on the elevated cold rims while it remains warmer at lower elevations inside the canyon. Shadows fall where they didn't before. Water shaped the land - it changed the climate - an array of new environments formed - new life moved in. As part of life, we now change the canyon with our dams and cause life to change. Everything is interconnected.

Part I - Water, Life and Earth
Section D
Water on Earth
• Intro - Blue Planet
• Stores of water
• Infinite cycle
• Sculpting the earth
• What's left to drink?
Quiz
Glossary
Resources
Teacher's guide
Information Sources
Contents

• Activity 3.1
World Heritage Sites
Find a world-class natural treasure near you!
UNESCO and the World Heritage Committee

UNESCO and the World Heritage Committee are "protecting natural and cultural properties of outstanding universal value against the threat of damage in a rapidly developing world."

Water plays a significant role in shaping many of these natural treasures. Threats to these sites are often related to our need for water and other resources. Get to know these places and be a part of the solution.

• Activity 3.2
USGS Geology in the Parks
Water plays an important role in shaping the most spectacular features in our National Parks. Explore these wonders of geology.
U.S. Geological Survey and National Park Service

• Activity 3.3
The Sun a Perfect Fuel
Learn more about how the Sun provides the Earth with energy - the energy that fuels practically every natural process on Earth.
The Sun a Perfect Fuel, Earthguide