Weathering and Erosion

Weathering and Erosion

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind and gravity. 

Erosion is the process by which soil and rock are removed from the Earth's surface by natural processes such as wind or water flow, and then transported and deposited in other locations.

(from Wikipedia the free encyclopedia)

Here are some great examples of natural Weathering and Erosion process  from http://science.nationalgeographic.com/

Arizona Rock Formation

Photograph by Melissa Farlow

Winds sweeping through the Grand Canyon have eroded this sandstone outcrop into an anvil shape. Wind shapes these fantastical forms by eroding less dense rock, like sandstone, faster than surrounding rock.

Badlands Thunderstorm

Photograph by Michael Collier

A thunderstorm does its part to shape Utah's Mussentuchit Badlands. Although this area gets only scant rainfall, over centuries, precipitation and wind have taken turns creating this rugged land's hundreds of gullies, ravines, and washes.

Baffin Island Waterfall

Photograph by Paul Nicklen

A waterfall fed by glacial runoff tumbles over sheer cliffs and into the turquoise water of Admiralty Inlet on Baffin Island, Nunavut, Canada. Such moving water is among the most powerful of nature's landscape-altering tools.

Bernard Glacier

Photograph by George F. Mobley

The Bernard Glacier in Alaska's Saint Elias Mountains looks like a huge alpine highway. Glaciers are slow but highly effective shapers of the land, essentially carrying away anything in their path—from soil and rocks to hills and even the sides of mountains.

Lichens on Granite

Photograph by Stephen Sharnoff

White lichens cover a blue granite gravestone like snow near Lake Champlain, New York. Lichens, symbiotic organisms that combine fungi and algae, can be powerful weathering agents, secreting chemicals called chelates that work to break down rock.

Limestone Swirls

Photograph by Jack Dykinga

Desert winds sculpted these gentle swirls out of the limestone hills in Black Gap Wildlife Management Area, Texas. This remote, 100,000-acre (40,470-hectare) area in West Texas contains some of the lowest, driest, and hottest areas in the Chihuahuan Desert.

Weathered Trees

Photograph by Richard Olsenius

Persistent winds in the mountains of Nevada's Great Basin National Park eroded the trunk of this old pine tree into what look like a pair of sideways spectacles. The Great Basin hosts drastically varied climates, from its cold, snowy mountains to its dry, hot desert valley.

Sand Tufa

Photograph by Larry Fellows, Arizona Geological Survey

With the snow-draped Sierra Nevada as a backdrop, unique erosion formations called sand tufa stand like giant cauliflower stalks in a dry Arizona lake bed. Before this alkaline lake went dry, tufa formed when a freshwater spring percolated from below and formed calcium carbonate deposits. When the lake's level dropped, these fragile formations surfaced, and wind went to work removing the sand beneath the deposits.

Sandstone Swirls

Photograph by Melissa Farlow

Wind erosion makes these layered sandstone hills swirl in Paria Canyon-Vermilion Cliffs Wilderness Area. The area, whose 112,500 acres (45,540 hectares) straddle the Utah-Arizona border, is home to sandstone arches, huge red rock amphitheaters, and hanging gardens.

Soil Erosion

Photograph by Lynn Betts, NRCS

Heavy rains in northwest Iowa washed away soil, leaving this scarred tableau. This type of erosion, termed sheet-and-rill erosion, occurs when there is insufficient vegetation to hold soil in place. As rain falls, it forms sheets of surface water that transport soil away. As more water accumulates, it forms runoff channels called rills, which further displace soil.

So, this weeks discussion was about weathering and erosion. The pictures may be amazing formations, and we can may wonder on how it occurs and sudden forms into great masterpiece of nature, but this could be worst and it could affect us humans..

Weathering and erosion slowly chisel, polish, and buff Earth's rock into ever evolving works of art—and then wash the remains into the sea.

The processes are definitively independent, but not exclusive. Weathering is the mechanical and chemical hammer that breaks down and sculpts the rocks.Erosion transports the fragments away.

Working together they create and reveal marvels of nature from tumbling boulders high in the mountains to sandstone arches in the parched desert to polished cliffs braced against violent seas.

Water is nature's most versatile tool. For example, take rain on a frigid day. The water pools in cracks and crevices. Then, at night, the temperature drops and the water expands as it turns to ice, splitting the rock like a sledgehammer to a wedge. The next day, under the beating sun, the ice melts and trickles the cracked fragments away.

Repeated swings in temperature can also weaken and eventually fragment rock, which expands when hot and shrinks when cold. Such pulsing slowly turns stones in the arid desert to sand. Likewise, constant cycles from wet to dry will crumble clay.

Bits of sand are picked up and carried off by the wind, which can then blast the sides of nearby rocks, buffing and polishing them smooth. On the seashore, the action of waves chips away at cliffs and rakes the fragments back and forth into fine sand.

Plants and animals also take a heavy toll on Earth's hardened minerals. Lichens and mosses can squeeze into cracks and crevices, where they take root. As they grow, so do the cracks, eventually splitting into bits and pieces. Critters big and small trample, crush, and plow rocks as they scurry across the surface and burrow underground. Plants and animals also produce acids that mix with rainwater, a combination that eats away at rocks.

Rainwater also mixes with chemicals as it falls from the sky, forming an acidic concoction that dissolves rock. For example, acid rain dissolves limestone to form karst, a type of terrain filled with fissures, underground streams, and caves like the cenotes of Mexico's Yucatán Peninsula.

Back up on the mountains, snow and ice build up into glaciers that weigh on the rocks beneath and slowly push them downhill under the force of gravity. Together with advancing ice, the rocks carve out a path as the glacier slumps down the mountain. When the glacier begins to melt, it deposits its cargo of soil and rock, transporting the rocky debris toward the sea. Every year, rivers deposit millions of tons of sediment into the oceans.

Without the erosive forces of water, wind, and ice, rock debris would simply pile up where it forms and obscure from view nature's weathered sculptures. Although erosion is a natural process, abusive land-use practices such as deforestation and overgrazing can expedite erosion and strip the land of soils needed for food to grow.

                                                                       Checked By:  

Professor Crisencio M. Paner