My Science School

 

 

Which are the highest mountains in the world?

The world’s highest mountains are in the Himalaya-Karakoram range to the north of India. The Andes Mountains in South America cover a larger area but are not so high. The Himalayas contain 79 peaks that are over 7,500 m high. The highest of these is Mount Everest, which is 8,863 m high. At these altitudes, mountains are always covered in snow and ice, and there is little oxygen to breathe. Although Mount Everest is the tallest mountain when measured from sea level, Mauna Kea in Hawaii is actually the tallest if measured from its base. It reaches 5,818 m below the surface of the Pacific Ocean. From its base to its peak, Mauna Kea is 10,023 m high.

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On top of the world

After many years Mount Everest was finally conquered on May 29, 1953, when a Nepalese guide, Tenzing Norgay, and a New Zealander, Edmund Hillary, reached the highest point on the Earth’s surface. Since then, many people have climbed Everest, and all the world’s major peaks have been conquered. It is now possible to map mountains from the air so that mountaineering routes can be carefully worked out in advance. Also, equipment has improved so that sheer rock faces can be readily climbed. Altitude sickness and avalanches of ice and snow are now the main hazards faced by climbers. 

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How are mountains formed?

There are three main ways in which mountains can be formed. Volcanoes form mountains when lava from deep inside the Earth cools and hardens on the surface. Other mountains are formed when layers of rock are forced up into folds, or when rocks fracture to cause faults, allowing slabs of rock to be raised up. These movements are caused by the very gradual shifting of the land areas, which sets up stresses in the Earth’s crust. 

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Can water wear away solid rock?

Water itself cannot wear away rock, but tiny particles of grit carried in the water can eventually wear away the hardest rocks. It is this continuous wearing process that cuts valleys through mountains and hills. The faster the water flows, the more the grit it carries wears away at the rock. You can see the same process in action along the coast. There, rocks are worn away by the action of sand dashed against them by the waves. 

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What is a spring?

Many types of rock contain tiny holes like a sponge, in which rainwater collects. The water gradually sinks down and eventually flows out lower down. Water stored in such porous rocks sometimes bubbles to the surface in springs. They are usually found near the foot of hills. Spring water is often used for drinking because as it passes through rock, any harmful substances or germs are filtered out. On more level ground, spring water is found by digging a well to reach the underground water. Small outflows of water can lead to the formation of isolated bogs or marshes. 

What is a delta?

As a river reaches the sea its flow becomes slower, forming an area known as a delta. As the water slows the tiny particles of silt carried by the current settle to the bottom, forming mud banks. These make the river-bed shallower, so the water spreads out to form a wide estuary. In large rivers like the Danube, islands form among these exposed mud banks, and the river water trickles through a maze of small waterways. This region, which is rich in plants and other wildlife, forms the river’s delta.

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Uphill flow!

Water always flows down a river, but occasionally the flow is reversed. This happens only in very large rivers, when very high tides overcome the normal river currents. In narrow parts of the river valley the water begins to pile up, and eventually a wave called a tidal bore passes back up the river, sometimes for a great distance. This happens in the Amazon in South America, where there is a bore as high as 4.5 m. A smaller bore travels up the River Severn in England.

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Which is the world’s longest river?

The Nile in Africa and the Amazon in South America are the world’s longest rivers. The Nile is 6,670 km long, and the Amazon is 6,448 km long. It is difficult to give an exact length because these huge rivers split into tiny tributaries near their sources, and some of these dry up or change course.

The Amazon is by far the largest river because it carries more water than the Nile, Mississippi and the Yangtze put together. The Amazon is 140 km wide at its mouth, and up to 91 m deep in places.

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How does a river begin?

Most of the rainwater that falls on the land returns to the sea by way of rivers. Rainwater first soaks into the ground, but once the ground is saturated the excess water begins to run off in small streams. More water comes from melting ice and snow. Small streams gradually merge and become bigger, until they eventually form a river. The tiny streams that are the source of a river often begin in damp areas such as swamps or bogs, or may flow out of a pond or lake. Usually they are in hills or mountains, where the rainfall is heaviest. 

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What causes the tides?

Tides are caused by the gravity of the Moon. As the Earth spins round, the water in the oceans is ‘pulled’ towards the Moon slightly, making a bulge. There is a corresponding bulge on the other side of the Earth. Wherever the bulges are positioned it is high tide. In between the water is shallower and so it is low tide. High tides occur every 25 hours, because at the same time that the Earth is spinning on its axis, the Moon is travelling around the Earth once every 27  days. This means that high tide is about one hour later every day.

 

 

 

 

What is the continental shelf?

The shallow underwater plateaus of land surrounding the continents form the continental shelf. They slope gently down to a depth of about 180 m, after which they slope more sharply towards the deep ocean. The continental shelf can extend out from the coast for long distances, or it may be narrow, for example off the coast of Chile where the Andes Mountains plunge down into the Pacific with hardly any shelf. Usually the shelves are wider off low – flying regions. The continental shelf is a valuable resource, as most fish are found here. Also, there are plans to mine some of the minerals on the sea – bed in these shallow waters.

 

 

How deep are the oceans?

The depth of the oceans varies widely, but the deepest part found so far is called the Marianas Trench. This trench is a deep cut in the bed of the Pacific Ocean, and its depth is as much as 11,034 m. Even at this enormous depth, signs of marine life have been seen in the trench. In 1960 Dr Jacques Piccard and Lt Donald Walsh reached a depth of 10,911 m in a US Navy vessel, Trieste. The Pacific Ocean is home to nine of the ten deepest sea trenches. The exception is the Puerto Rico trench in the western Atlantic Ocean, which has a maximum depth of 9,220 m.

 

 

 

 

Why did sailors fear the Sargasso Sea?

Sailors feared that the Sargasso Sea was haunted by sea monsters and filled with seaweed that would entangle their ships and prevent their escape. The Sargasso Sea is a patch of ocean in the North Atlantic, about 3,200 km west of the Canary Islands. The ocean currents in this area are very slow, although they are surrounded by fast moving currents. This means that any seaweed floating in the Sargasso Sea will not be carried away. Patches of floating weed can be as large as 30 m in diameter. Despite the legends, they are never thick enough to entangle a ship.

 

 

Why is the sea salty?

A mixture of salty substances is washed out of rocks by rivers and deposited in the sea. When rain falls on the land it gradually dissolves minerals. The dissolved salts slowly enter rivers and streams, and are carried down eventually into the sea. This process is happening all the time, and so the oceans and seas gradually become more salty.

 

 

 

 

 

 

What is the Gulf Stream?

The Gulf Stream is an ocean current that controls the climate and weather of the whole of Europe. The current starts in the Gulf of Mexico, carrying warm water across the Atlantic and travelling northeast until it reaches the European coast. Water evaporates from the surface of the Gulf Stream causing rainfall in Western Europe.

 

 

 

Continue reading " Oceans"

               In the Elephant Island, Shackleton’s party divided into two. Twenty one men were asked to stay back on the island. Shackleton left the island with five chosen rowers, to find a way out and to come back and rescue the members stranded on the Elephant Island.

               Shackleton braved the Southern Ocean for 16 days. Soon, they made a landfall. Unfortunately, three members of the party were too sick and exhausted to continue. Shackleton and the two others climbed the icy mountains. At last they reached their destination on South Georgia Island. Shackleton succeeded in chartering a steamship to rescue his men.

               On 30th August 1916, Shackleton managed to return to the Elephant Island. And he rescued his men from the Elephant Island. 

              Ernest Shackleton set out on the ‘Imperial Trans-Antarctic Expedition’ in 1914. The expedition faced terrible hurdles throughout the journey. Their ship ‘Endurance’ became beset in the ice of the Weddell Sea on the way. He and his crew were forced to spend the whole of the 79 days of the winter there. Finally, the crew was forced to abandon the ship, because it was about to be crushed by the ice.

               However, they had saved a large quantity of food and gear, as well as their three boats. For three months the ice floes took them further to the north. Food shortage became acute as weeks passed. They caught seals and ate their meat. So they could conserve the remaining packaged rations. The most dangerous thing was the cracking up of ice. Sometimes, huge killer whales charged up from below, and sought to attack them.

               Later, Shackleton found that instead of making good progress westwards, they had actually travelled 48 kilometres to the east, as a result of the drifting ice. However, they finally made a landfall on an uninhabited island known as the Elephant Island. 

               Sir Ernest Henry Shackleton was an Irish born polar explorer who led three British expeditions to the Antarctic.

               In 1901, Shackleton joined his first expedition to the Antarctic. Unfortunately, he was sent home early due to bad health, after he, and his companions Scott and Edward Adrian Wilson set a new southern record by marching to latitude 82°S.

               In 1914, he set off on his own expedition to Antarctica. Shackleton was in a race with Roald Amundsen to reach the South Pole. The race ended in December 1911, with Roald Amundsen’s conquest.

               Shackleton later planned a voyage to the South Pole, and while returning, he wanted to pick a different route to the Ross Sea, and thus, become the first person to cross the Atlantic Ocean.

               To this end, he made preparations for what became the Imperial Trans-Antarctic Expedition. On 1st August 1914, Shackleton departed London on the ship ‘Endurance’ for his voyage to the South Pole. There were unimaginable hurdles throughout the voyage, which Shackleton overcame with his will power, and leadership quality. 

            Robert Edwin Peary, an American explorer, known for his discovery of the geographic North Pole, was one of the greatest polar explorers. Peary made several expeditions to the Arctic in the late 19th and early 20th centuries. Peary was one of the first Arctic explorers to study Inuit survival techniques, which he used to his great benefit.

            After many failed attempts, Peary decided to set out on a final voyage. Peary and 23 men set off from New York City on 6th July 1908, under the command of Captain Robert Bartlett.

            They spent their winter near Cape Sheridan on Ellesmere Island. He reached the North Pole with his expedition on 6th April 1909. But, it is now suspected that he might have been 48 to 96 kilometres short of the Pole, but is still credited with the achievement.

            His success is widely disputed today, but his effort was noteworthy. Peary was promoted to the rank of Rear Admiral in the Navy Civil Engineer Corps on 6th April 1909, and retired the same day.

            Admiral Robert Peary died in the US, on 20th February 1920. 

 

               Robert Scott, a British Royal Navy officer and explorer, led two expeditions to the Antarctic region, at the same time as Amundsen.

               Roald Amundsen and Robert Scott took on a gripping race through danger to reach the South Pole. Amundsen reached the South Pole on 14th December, and became the first person to reach the South Pole. Robert Scott reached his destination on 17th January, only to see Roald Amundsen’s Norwegian flag waving their gloriously. However, Robert Scott’s return journey turned out to be a catastrophe, as they were too late to travel because of the deteriorating weather conditions.

               Robert Scott and his entire crew froze to death. Scott is presumed to have died on 29th March 1912. Eight months later, a search party found the bodies, which were buried under the base tent. News of Scott’s death reached the world on the 10th of February, 1913.

               After confirming the legend’s death, the British government recognized him as a national icon.

               However, the reasons behind the fate of Robert Scott and his team were identified as lack of polar knowledge and poor planning skills.

 

               Amundsen planned to sail to the North Pole, and explore the Arctic Basin. But, later he decided to reroute to Antarctica. He kept this as a secret from everyone except his brother, who knew that Amundsen was heading to the South Pole, instead to the North.

               Roald Amundsen even made his crew believe they were embarking on an Arctic voyage, and revealed their destination only when the expedition was leaving their last port of call.

               He set up his Antarctic base in the Bay of Whales, on the Great Ice Barrier. The base was 96 kilometres closer to the Pole than the base of the English explorer Robert Scott, who was heading a British expedition at the same time. But Amundsen was more skilful and he used skis and sledge dogs which ensured rapidness. Robert Scott used Siberian ponies, instead of sledge dogs but they failed to brave the weather. 

 

               Roald Amundsen, from Norway, is one of the world’s most famous polar explorers. He was the first person to sail through the North-West Passage which is the seaway across the Arctic, linking the Atlantic and the Pacific Oceans.

               When Amundsen and his crew progressed through the dangerous course and passed through the North-West Passage, they realized that they had navigated the much sought after North-West Passage. They sighted a whaling ship from San Francisco there.

               Amundsen and his crew were jubilant as they crossed the passage, which had defeated so many seamen for many centuries before them. The Gjoa, Amundsen’s ship, became the first vessel to transit the passage.

               However, more struggles were ahead, as they continued their voyage. His ship got trapped in the ice again. However, the Gjoa passed through the Bering Straits in 1906, and only then could Roald Amundsen claim to be the first to navigate the North-West Passage.