Abdul Wahab - science4fun

Continents are large masses of continuous land above sea level. The land surface of our Earth has been divided into seven continents; Asia, Africa, North America, South America, Europe, Australia, and Antarctica. Geographically, each continent is divided into many countries, for example, Asian Continent has 48 recognized countries by United Nation.

How Continents Are Divided?

Our Earth has been divided into seven continents geographically. These seven continents are not divided based on the pure scientific definition. For example, it is assumed that our 7 recognized continents are distinct masses of land. But in reality, only Antarctica and Austria are the only separated land masses. Other continents are somehow connected e.g. Asia is connected with Africa by a 125 km wide land bridge called the Isthmus of Suez.

Furthermore, Europe and Asia are a single largest landmass called Eurasia. But still, they are recognized as separate continents by cultural and language differences. If we strictly follow the distinct landmasses definition of continents. Then we will be left with only four continents which are Afro-Eurasia, America, Australia, and Antarctica.

Microcontinents

Many Islands and other small distinct landmasses that are too small to be recognized as continents are called microcontinents. These are the fragments of ancient large continents, also called supercontinents, from which present-day continents are formed. Madagascar is one of the famous microcontinents.

Subcontinents

Indian-Subcontinent-Map — Indian subcontinent

Main continents are often subdivided into subcontinents. For example, Asia is divided into the Indian subcontinent, Arabian Peninsula, Indochinese Peninsula, Japanese archipelago, and Maritime Southeast Asia. In many cases, subcontinents often lie on different tectonic plates than their parent continent. America, as a single continent, is subdivided into North America, South America, and Central America subcontinents.

How Continents Were Formed?

Pangaea-Supercontinent — Pangaea supercontinent – 240 million years ago

The surface of the Earth (including the land and oceanic floor) is composed of many pieces that are joined together like a jigsaw puzzle that floats on the mantle layer of the Earth. These pieces are called plate tectonics which are under constant movement since the formation of the Earth. The present-day continents, as seen today, were not in the same place and shape in the past. The position, size, and shape of these continents have been changing due to plate tectonics activity.

Around 480 million years ago, the Earth had many distinct continents that were mostly scattered south of the Equator. But 240 million years ago, all these continents were merged and formed a large chunk of land called the Pangaea Supercontinent. Around 40 million years later, the Pangaea began to break apart due to plate tectonic activities. This was the beginning of the formation of the modern continents that we see today. In the next 200 million years, the continents were shaped and placed where you see them on the map.

The development of continents is not stopped yet, they are still moving at the speed of 2 cm per year. If you fast forwards the time, you will see California will be detached from North America and will become an island.

Interesting Facts

The word Continent land means continuous land was translated from the Latin words terra continens. Also, the word continent land means a connected land.
Asia is the most populous and largest continent in size.
Africa is on the top of the list by the number of countries. It has around 54 countries including South Africa, Egypt, Sudan, Nigeria, and Somalia.

The Southern Ocean is the 4^th largest Ocean among the five major oceans. It is also known as the Antarctic Ocean because it completely encloses the Antarctica continent. The Southern Ocean covers around 6% area of the Earth. The Southern Ocean was recognized recently in 2000 as a separate ocean. Earlier, its regions were considered the parts of the Pacific, Atlantic, and Indian Oceans.

Characteristics

Water Circulation

The Southern Ocean has a unique and most powerful oceanic current, called Antarctic Circumpolar Current. It circulates clockwise and constitutes the world’s longest ocean current having a length of 21,000 kilometers. This circular motion of the current keeps the warm water of surrounding oceans away and helps the Antarctica continent maintain its low temperature.

Temperature

The temperature of the Southern Ocean varies according to the season from -2 °C to 10 °C. In winter, the ocean’s surface gets frozen near the Antarctica Continents.

Salinity

The salinity level of the Southern Ocean changes as you go away from Antarctica land. It has been found that salinity near the Antarctica land is decreasing due to the increased melting of glaciers over the past few decades.

Natural Resources In The Southern Ocean

The Southern Ocean is believed to have large deposits of oil and natural gas near the continental land. Also, the large deposits of gold are expected to be found beneath the floor of the ocean. The possible reason for the deposition of gold in the ocean was gravity separation in sedimentary processes.

Who Lives There?

The Southern Ocean contains many smaller and large icebergs throughout the year. A large variety of living things including Animals, Birds, and fishes dwell on the Antarctica mainland, surrounding icebergs, and underwater. Some of the living creatures are phytoplankton, whales, penguins, seals, orcas, albatross birds, and cod icefish.

Effects Of Climate Change

The Southern Ocean is the region on Earth that receives the rapid impact of global climate change. A slight change in the temperature causes a huge perturbation in the environment. This includes rapid changes in the weather, increased oceanic temperature, and melting of glaciers and icebergs. These climate change effects impact almost all living species in that region.

Interesting Facts

The largest invertebrate, known as the colossal squid, lives in the Southern Ocean. They can grow to a length of 14 meters. Also, the colossal squids have the largest eyes of any creature which can grow to 27 centimeters in diameter.
The deepest place in the South Ocean, known as the South Sandwich Trench, is about 7.2 kilometers deep. However, the average depth of the southern ocean is 3.2 kilometers.
Antarctica and the Southern Ocean together constitute around 90% of our Earth’s ice.

The Indian Ocean is the 3^rd largest ocean among the five major oceans of the Earth. It covers around 19.8% of our Earth’s surface. The Indian Ocean has been named after India – a country. The main reason for keeping its name after India is due to the country’s largest shoreline with the Ocean. The Indian Ocean is surrounded by four continents; Asia, Africa, Antarctica, and Australia.

Characteristics

Temperature

The Indian Ocean is the warmest of all the other major oceans. Its temperature is highest at the equator and coldest near southern Africa and Australia. The average temperature near the equator is around 28°C. Since 1901, there has been a continuous increase in the temperature of the Indian Ocean. According to researchers, the increase in temperature is due to the emission of greenhouse gases across the globe.

Salinity

Indian Ocean’s salinity is highest in the northern region, known as the Arabian Sea, due to the higher amount of evaporation and low precipitation. However, the salinity drops from the north region towards the southeastern region. The least saline region of the Indian Ocean is the Bay of Bengal. It has less salinity due to the inflow of freshwater rivers and a higher amount of precipitation.

Water Circulation

There are two main gyres (systems of circulating ocean currents) in the Indian Ocean. One is in the northern part which flows in the clockwise direction, and the second is in the southern part which flows in the anticlockwise direction. These ocean currents are highly affected by monsoon (seasonal changes in precipitation and circulation of the atmosphere).

Waterways

The waterways in an Ocean or a Sea are routes that connect different Oceans and Seas. The Indian Ocean has four major waterways; The Suez Canal, Bab el Mandeb, the Strait of Hormuz, and the Strait of Malacca. Among these waterways, the Suez Canal is the busiest and most used waterway that connects the Red Sea (region of the Indian Ocean) to the Mediterranean Sea for transporting goods from Asia to Europe.

Islands of the Indian Ocean

There are about 1,382 islands in the Indian Ocean including habited and inhabited. Among these Islands, the five larger Islands are Madagascar, Sri Lanka, Grande Terre, Nias, and Socotra. Madagascar and Sri Lanka are the independent Island countries

Tsunami Of 2004– World’s Deadliest Disaster

A tsunami is a sequence of powerful waves in the ocean generated by earthquakes or underwater volcanoes. In December 2004, a powerful earthquake happened in Indonesia with a magnitude of 9.1. Due to this, the most powerful tsunami in the past 40 years was generated in the Indian Ocean. Around 14 countries were affected by this tsunami and a total of 225,000 people were killed.

Interesting Facts

The Java Trench is the deepest place in the Indian Ocean. Its depth is 7,187 meters, which is 65% of the Mariana Trench whose depth is 11,000 meters.
The Indian Ocean is also referred to as the landlocked Ocean because its northern part is locked by Asian Continent.
Due to high evaporation and low precipitation, the Indian Ocean has a lower amount of dissolved oxygen as compared to other major Oceans.

The Arctic Ocean is the smallest and most frozen Ocean on the Earth. It is entirely frozen in winter and melts partially in the summer months. Earth’s geographic and magnetic North Pole also lies in this Ocean. The Arctic Ocean’s name is derived from the Greek word “Arktos” which means bear. The reason for giving that name is because polar bears live in this region.

The Arctic Ocean covers only 4% of Earth’s surface and it is about 1.5 times the size of the USA, or 80% the size of Russia. It is bounded by Europe, Asia, and North America. The Arctic Ocean is the shallowest ocean among the five major oceans at an average depth of 1 kilometer. However, the deepest place in the Arctic Ocean is about 5.5 kilometers deep and is called “Molloy Hole”

Characteristics

Temperature

The Arctic Ocean is the coldest among the five major oceans and is completely frozen in the winter months. During the summer months, layers of ice melt down completely in some regions and ocean water becomes visible. Moreover, ice from the glaciers and ice shelves also shrinks in summer. The melting of ice makes the ocean surface texture darker which increases sunlight absorption.

Salinity

The Arctic Ocean is the least saline ocean due to several reasons and its salinity also varies significantly according to the season. The main cause of lower salinity is lower evaporation and a high inflow of freshwater rivers from glaciers. The salinity becomes even low in summer due to the heavy melting of glaciers.

Who Lives on the Arctic Ocean?

bear-on-glacier — Polar Bear on the ice of Arctic Ocean.

The Arctic Ocean’s surface is frozen and consists of massive glaciers. There is a variety of animals that live on the surface of the Arctic Ocean and also underwater. Some of the famous animals are polar bears, walrus, Dall sheep, seals, moose, caribou, beluga whale, and arctic wolf.

The Arctic Ocean is bounded by several countries, some of which are the USA, Canada, Greenland, Iceland, Norway, and Russia. Some regions of these countries come inside the boundaries of the Arctic Ocean. People living in the region of the Arctic Ocean are about 4 million.

Shrinking Ice of Arctic Ocean

Arctic-Ocean-ice-1980-to-2010 — The Arctic Ocean ice from 1980 to 2010

In the past few decades, the Arctic Ocean’s glaciers have been continuously shrinking due to an increase in average temperature. As the ice shrink, more ocean water becomes visible which reduces the reflection of the surface. As a result, more and more heat is absorbed by the dark-colored ocean which further increases heat and sped-up the ice melting. This is called the run-away effect which is majorly caused by global warming.

Interesting Facts

B-15 Iceberg is the largest iceberg in the Arctic Ocean whose area is 11,000 sq. Km.
The Arctic Ocean is governed by international law “The Law of the Sea Treaty” and is not controlled by any one nation.
Researchers believe that 25% of Earth’s crude oil reserves are buried under the Arctic Ocean’s crust.

Mount Rushmore is one of the famous mountains in South Dakota, located in the black hills mountain range. It is famous due to the large sculptures of four famous presidents of the United States. These presidents are Abraham Lincoln, Theodore Roosevelt, George Washington, and Thomas Jefferson. Mount Rushmore receives around 3 million international tourists every year.

How Sculptures on Mount Rushmore Were Formed?

Doane Robinson was a historian who had an idea to somehow promote the tourism in South Dakota State of the US. He thought to form sculptures on one of the mountains in the black hills. He convinced the sculptor Gutzon Borglum in 1924 to carve the sculptures. Gutzon Borglum had chosen Mount Rushmore for carving sculptures because it receives maximum sunlight throughout the day in the black hills. The sculptures of Mount Rushmore were finished in 1941 and many sculptors have contributed to them.

Furthermore, it was proposed to add the fifth sculpture of one of the US presidents. But after the survey, it was found that the rocks of the mountain will not be able to support the fifth sculpture. If further sculpting is done on the mountain, the four remaining sculptures can become damaged.

Geology of Mount Rushmore

Mount Rushmore is mostly composed of granite (a type of igneous rock). Around 500 million years ago, Mount Rushmore eroded which shrunk its size. In the next 200 million years, the sandstone buried the whole mountain. Until recently around 70 million years ago, the mountain was again re-exposed in some geological activities.

One of the reasons for making sculptures on Mount Rushmore was its erosion resistance. It erodes very little as compared to other mountains in the Black Hills. It has been estimated that Mount Rushmore erodes around 1 inch every 10,000 years. This makes it suitable to hold the sculptures for a longer time.

Interesting Facts

The Sculptures cost around 989,992 dollars in 1941. If you take inflation into account then these are around 17 million USD in 2020.
The peak of Mount Rushmore reaches 5,725 feet high.
The height of presidents’ faces in Mount Rushmore is about 60 feet.
“Hall of Records” is the secret room behind the head of Abraham Lincoln’s face sculpture. The secret room contains documents about the information of Mount Rushmore and the US history.