Continents: 7 major land divisions on Earth
When geographers recognize a continent they usually include all the related islands. Japan, for example, is a member of Asia. Similarly, Greenland and all the Caribbean Sea islands are commonly considered a part of North America. The continents together add up to some 148 million square kilometres (57 million square miles) of land.
How were continents formed?
To understand this we need to understand the theory of continental drift.
Continental drift theory is an attempt to understand how continents and oceans are organized today.
1. In this theory, it is assumed that at the beginning all continents were united and formed a single large unit of the landmass.
2. This 'stable' or 'parent continent' is known as 'Pangaea’.
3. The word Pangaea is made up of two different parts called “pan” which means “all” and “Gaea’ meaning “earth”.
4. The Pangaea started to break up close to the end of the Mesozoic period.
The reason for the breaking down of Pangea was given by a German meteorologist and geophysicist Alfred Wegener who put forward a hypothesis known as the continental drift hypothesis which states that all the continents formed a single continental body, and the globe was surrounded by a superocean.
According to Wegener:
- The supercontinent of Pangaea began to split around 200 million years ago to form ‘Laurasia’ (which included modern-day North America, Greenland and all of Eurasia and ‘Gondwanaland’ ( which includes modern-day South America, Africa Madagascar, India, Arabia Malaysia East Indies, Australia, and Antarctica ).
- These two landmasses were separated by a long shallow inland sea known as the ‘Tethys Sea’. It is considered that the present shapes and the relative positions of all the continents are the results of the fragmentation of ‘Pangaea’ by rifting and drifting apart of the broken landmasses.
- The reason behind this fragmentation is the movement of tectonic plates (earth crust floating over hot lava of molten mantle).
Tectonic Plates are still in motion even today, moving at a very slow rate.
Details about 7 continents(approx)
Name of the Continent
Number of Countries
44,579,000 sq. km
30,221,532 sq km
24,709,000 sq km
17,840,000 sq km
14,000,000 sq km
10,180,000 sq km
8,525,989 sq km
Features of Mountains
|1||A mountain is a geological land type rising above the surrounding landform.|
|2||A mountain usually rises at least 1,000 feet above sea level. Some mountains exceed 10,000 feet above sea level, with Mount Everest being the world's highest mountain at an altitude of 29,036 feet.|
|3||Tiny mountains are typically called hills (below 1000 feet).|
|4||These are usually formed by the tectonic plate movement in the Earth's crust. Large mountain ranges like the Himalayas also form along those plate boundaries. Tectonic Plates move very slowly and since mountains are formed due to tectonic movements, it can take millions of years to form a mountain.|
Types of Mountains
There are three main types of mountains viz.
|Serial No.||Types of Mountains|
|2.||Fault Block Mountains|
These mountains are named according to the mode of formation.
|Types of Mountains||Features|
1. Fold Mountains are created when two plates collide or run into each other.
|Fault-block Mountains||1. Fault-block Mountains develop along Faults where some large blocks of rock are pushed upwards while others are forced down.|
2. Sometimes the higher area is called a "Horst" and the lower one a "graben".
3. In the western United States, the Sierra Nevada Mountains are examples of fault-block ranges.
|Volcanic Mountains||1. The volcanic mountain ranges are called volcanic ranges. |
2. Two major types of volcanic mountains that exist are volcanoes and the Dome Mountains. Volcanoes form as magma erupts all the way up to the Earth's surface.
3. The magma can on the surface of the Earth gets hardened and in this process forms a mountain.
4. Dome Mountains are formed when a great deal of magma rises up below the surface of the Earth. It forces the rock above the magma to gush out and form a mountain. 5. Examples of volcanic mountains include Mt. Fuji and Mt. At Hawaii Mauna Loa.
Details about the 5 Highest Mountains of the world
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