Forces of the Earth: Water

Most of the Earth is water, about 97 percent of it in the ocean. Clouds carry water droplets inland by weather systems, and when the water droplets become too big, they fall as rain, hail, or snow, depending on the temperature. This is when water meets land, waters it, erodes it. As water fall on streams, it flows into rivers which then cut into the rocks on the riverbed and land on either side. Over eons of time, this process of erosion can create spectacular effects. A famous example: in the US, the Colorado River has sliced down through rocks representing two billion years of Earth’s history, forming the Grand Canyon in Arizona.

One of the most intriguing and perhaps, slightly bizarre landforms to be found in a canyon is the ‘hoodoo.’ It is formed because different rock types erode at different rates. Dolomite, limestone and siltstone, for example, are hard, while mudstone is soft. One of the best places in the world to see hoodoos is Bryce Canyon National Park in Utah.

On their way to the sea, rivers not only cut through the rocks to form valleys, canyons and gorges, but also erode the bedrock on the riverbed to create waterfalls. Here, the river tumbles over a vertical drop of a series of drops, and the result can be sensational as can be seen in Angels Fall in Venezuela, the Ruacana Falls in Namibia, or the Gullfoss and Dettifoss in Iceland. The last two are ‘multi-step’ waterfalls in which there is a series of falls of roughly the same size, each with its own plunge pool.

Eventually, all that water is returned to the sea, completing the water cycle. Indeed, some waterfalls plunge directly into the sea. Back into the ocean, water turns back on itself and attacks the land as when waves slam into cliffs or when rock fragments are picked up by the waves and thrown against them, causing them to collapse.

Tumultuous seas swept by fierce winds can reshape rocks into sea stacks, some of which are towering pillars that seem to rise mysteriously from the deep. On Foula, the most westerly island in the remote Shetland in the north of mainland Scotland, wave action has resulted in the formation of spectacular sea stacks standing where softer rocks in a promontory have been eroded, leaving behind the harder rock.

Leonardo da Vinci’s famous quote that “with time and water, everything changes” is an apt description of the power of natural water as a agent of change, as we saw in the above description and as you will see in the images below.

The ‘Candle’ is a rock formation in the upper part of Antelope Canyon, near Page, Southwest Arizona. This slot canyon, with its 40m high walls, is in two sections: the upper and the lower. Shafts of direct sunlight illuminate the upper section but only for half the year. The lower section of Antelope Canyon is known appropriately as ‘The Cockscrew’. The rock has been eroded smooth and the passageways contorted into spiral rock arches by flash floods, wind and rain. See the next image.

Like a great army of giants, hoodoos stand to attention in Bryce Canyon National Park, Utah. These are tall, thin spires of rock that protrudes from the bottom of an arid basin or badland that have been weathered by frost, water and wind.

Aerial view of hoodoos in Bryce Canyon National Park.

Conifer trees cling to the steep walls of the Grand Canyon of Yellowstone National Park, Wyoming. The area below the Lower Falls was once a geyser basin, and the heat made the rocks softer, and therefore more easily eroded. The process was accelerated during the Last Ice Age when ice dams burst and caused flash floods to barrel down the valley, sweeping the rocks away.

The Kunene River plunges 120m over the Ruacana Falls in northern Namibia. The falls are at their best when water is released from Angola’s Calueque Dam, 20km upstream. They are said to rival Victoria Falls for pure spectacle.

Ethiopia’s Sof Omar Cave is possibly the longest in Africa. It has been carved out of the rocks by the action of the Weyib River, creating a series of vaulted chambers and natural underground arches that resemble Gaudi’s cathedral in Barcelona.

Rocky outcrops weathered by the action of the waves are scattered off the coast of Foula, or ‘bird island’. Foula is one of the most remote inhabited islands in the Shetland archipelago of Scotland. Just 38 people live here permanently, their ranks swollen in summer by birdwatchers and hikers.

The sky is reflected in a small pool in marble bedrock in Lahlo National Park, Norway. The park is known for its water-eroded caves, swallow holes and alpine karst landscapes where rivers simply vanish underground, before reappearing downstream.

Backlit by the setting sun, the towering Reynisdrangar sea stacks in Iceland are made of volcanic basalt and eroded slowly by the sea.

Northern Iceland’s Dettifoss is thought to be the most powerful waterfall in Europe. The river flows from the Vatnajokull glacier, the largest in Europe, and is greyish white because of the sediments it carries. The falls themselves are 100m wide, with a drop of 45m. They appeared in the 2012 film Prometheus, the stark and dramatic scenery forming an alien landscape.

Gullfoss, meaning ‘golden falls’, is Iceland’s most spectacular waterfall. In a dramatic display of nature’s power, the waters of the Hvita River tumble down a three-step staircase, turn sharply, and then plunge into a steep canyon.

The Green River is a tributary of the mighty Colorado River. They have both carved deep canyons into the Colorado Plateau. Their confluence in the Canyonlands National Park, Utah is a striking prelude to the famous Grand Canyon downstream.

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