Category Geography

WHICH IS THE LARGEST GLACIER?

The world’s largest glacier is the Lambert glacier in Antarctica, according to the United States Geological Survey. The glacier is more than 60 miles (96 km) wide at its widest point, about 270 miles (435) long, and has been measured to be 8,200 feet (2,500 meters) deep at its center.

Glaciers form when the annual snowfall in a region exceeds the rate at which the snow melts, allowing enormous amounts of snow to accumulate over time. The fallen snow compresses into solid ice under its own weight, forming solid sheets of ice.

And these sheets are in motion. Glaciers flow like very slow-moving rivers, and can stretch over hundreds of miles. The Lambert glacier flows at a rate of about 1,300 to 2,600 feet (400 to 800 meters) each year.

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WHAT ARE GLACIERS?

The word glacier comes from the French word glace, meaning ice. A glacier is a huge, slow-moving mass of ice. Glaciers are generally seen in mountainous regions where temperatures always remain close to freezing and a massive amount of ice accumulates. Forced by the weight of the ice and the pull of gravity, these sheets of ice start moving, almost like a river, although most glaciers move no more than one  centimetre a day.

Glaciers are massive bodies of slowly moving ice. Glaciers form on land, and they are made up of fallen snow that gets compressed into ice over many centuries. They move slowly downward from the pull of gravity.

Most of the world’s glaciers exist in the polar regions, in areas like Greenland, the Canadian Arctic, and Antarctica. Glaciers also can be found closer to the Equator in some mountain regions. The Andes Mountain range in South America contains some of the world’s largest tropical glaciers. About 2 percent of all the water on Earth is frozen in glaciers.

Glaciers can range in age from a couple hundred to thousands of years old. Most glaciers today are remnants of the massive ice sheets that covered Earth during the Ice Age. The Ice Age ended more than 10,000 years ago. During Earth’s history, there have been colder periods—when glaciers formed—and warmer periods—when glaciers melted.

Scientists who study glaciers are called glaciologists. Glaciologists began studying glaciers during the 19th century in order to look for clues about past ice ages. Today, glaciologists study glaciers for clues about global warming. Old photographs and paintings show that glaciers have melted away from mountain regions over time. Indeed, glaciers worldwide have been shrinking—and even disappearing—at an accelerated rate for the past several decades.

Credit: National Geographic Society

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HOW DO WATERFALLS FORM?

A waterfall develops when the bed of the river changes from hard to soft rock. As the force of the water wears away soft rock faster, the level of the softer riverbed drops, and the river plunges over a ledge of hard rock. The depth of the fall increases over time as more and more of the soft rock is washed away.

A waterfall is a river or a body of water that steeply falls over a rocky edge into a plunge pool. These are also called cascades.

Erosion is the process of wearing away the earth. It plays an important part in the formation of waterfalls. Waterfalls also contribute to erosion.

The process of formation of waterfalls happens when a stream flows from soft rock to hard rock. This happens both laterally and vertically. In every case the soft rock erodes and leaves the hard rock as it is. Over this a stream falls.

The fall line is an imaginary line along which parallel rivers plunge while flowing from uplands to low lands. Many waterfalls in this way help the geologists determine a region’s fall line and underlying rock structure.

As the stream flows it carries various amounts of sediments- be it microscopic silt, pebbles or boulders. Sediments erode the beds of soft rocks like sandstone or limestone. The stream then cuts the beds so deep that only hard rocks like granite are left.

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HOW DO RIVERS KEEP FLOWING?

Rivers are kept running by the addition of water from rainfall or melting snow. Even when it does not rain, underground reservoirs (water stores) keep rivers supplied with water and flowing. When it rains, a lot of water seeps and sinks into the ground to surface somewhere else as a spring. Over thousands of years, rivers can carve huge valleys out of solid rock with a wide floodplain, which is a flat area that catches the overflow when the river is full.

Rivers keep flowing because gravity is constantly pulling the water down the path of least resistance (downhill). A river flows because there is a water table to support it. A river is nothing more than an outward manifestation of the water table.

A river that does not run dry at any time of year is carrying surplus water from precipitation that collects in the permeable rocks of hills and mountains that surround the watershed. Most rivers get their water from the mountains, where there is far more precipitation than over the lowlands.

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WHICH IS THE HIGHEST WATERFALL?

Angel Falls or Salto Ángel (indigenous name: Kerepakupay Vená) is the world’s highest free-falling waterfall at 3,212 feet with an uninterrupted drop of 2,648 feet lying in the Canaima National Park, Venezuela. It is situated on the Churún River, an affluent of the Carrao. Curún in indigenous Pemón language means “thunder.”

Angel Falls is located in the Guayana highlands, one of the five topographical regions of Venezuela. It plunges off the edge of a tepui, or table-top mountain, called Auyan Tepui (“Devils Mountain”). It is 500 feet wide at its base and in total is 15 times higher than America’s Niagara Falls Angel Falls in Venezuela, which plunge 979 m vertically.

Angel Falls is one of Venezuela’s top tourist attractions, despite its remoteness and the absence of roads leading to nearby villages. One of the world’s great natural wonders, Angel Falls inspires feelings of awe in the hearts of those who make the journey.

Although sighted in the early twentieth century by the explorer Ernesto Sanchez La Cruz, the waterfall was not known to the Western world until it was visited in 1935 by the American aviator, James Crawford Angel, on a flight while searching for a valuable ore bed. In 1936, he returned and landed his plane at the top of the waterfall. The falls are currently named “Angel Falls” after him; interestingly, the indigenous name for the falls means “Devil’s Mouth.”

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WHICH IS THE WORLD’S LONGEST RIVER?

Flowing northward through the tropical climate of eastern Africa and into the Mediterranean Sea, the Nile river is the longest river in the world at 4,135 miles (6,650 kilometers), according to the U.S. National Park Service.

The Nile runs through Egypt, as well as nine other African nations Sudan, Eritrea, Ethiopia, Uganda, Kenya, Tanzania, Rwanda, Burundi and the Democratic Republic of Congo. More than 300 million people depend on the Nile for their water supply and the irrigation of seasonal crops, according to the Council of Ministers of Water Affairs of the Nile Basin.

The Nile’s energy is harnessed by the Aswan High Dam, which was completed in 1970 and provides hydroelectricity and controls summer flooding. During the 1980s, the dam provided half of Egypt’s electricity, although that amount has decreased over the years and it currently contributes 20 percent of total energy generated in Egypt, according to NASA’s Earth Observatory.

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