• Plutonic rocks:  These are formed at some depth of the earth’s crust. They have cooled and solidified slowly so that large crystallines have been formed. These intrusive rocks such as granite, diorite and gabbro are exposed at the surface by the process of erosion and denudation.
• Volcanic rocks: These are molten rocks poured out of volcanoes as lava. They solidify rapidly on the earth’s surface and the crystals are small. Basalt is a common volcanic rock which forms into lava flows, lava sheets etc. Deccan plateau in India, Columbia snake plateau in U.S.A. If lava solidifies vertically it’s called dykes and if it solidifies in the horizontal format it’s called sills

Sedimentary rocks

Sedimentary rocks are formed with sediments which are accumulated over a long period, usually, they are underwater. These sediments are brought by rivers, glaciers, winds or animals. These sediments generally contain fossils of animals, plants and other micro-organisms. Sedimentary rocks can be classified according to their age, those are

• Mechanically formed sedimentary rocks: These rocks have been formed with an accumulation of materials derived from other rocks which have been cemented together. Sandstone comes as a significant example of sedimentary rock under this category. Sandstone is made of sand grains, and quartz which are derived from granite. When large pebbles are firmly cemented to form a rock is called a conglomerate. The finer sediments are forms of clay and they are used in making clays. 
• Organically formed sedimentary rocks: These rocks are formed from the remains of living organisms such as corals, and shellfish. The most organically formed are of calcareous- limestone and chalk. The rocks which are formed out of vegetative remains are called carbonaceous.
• Chemically formed sedimentary rocks: These rocks are formed from chemically precipitated solutions of one or other. Ex: gypsum is formed with the evaporation of salt lakes. 

Metamorphic rocks

Metamorphic rocks are formed when rocks are subjected to high heat, high pressure, and mineral-rich fluids. These rocks started as different types, but have been substantially changed from their original igneous, sedimentary or earlier metamorphic form. Examples of metamorphic rocks are – phyllite, schist, gneiss, quartzite and marble. Pressure or temperature can even change previous forms of metamorphic rocks into new types. 

3. Types of mountains

Mountains occupy a significant portion of the earth’s atmosphere. These mountains can be classified according to the way they have been formed. There are four types of mountains: Fold mountains, Fault-block mountains, Dome mountains and Plateau mountains. 

• Fold Mountains: These are the most common mountains around the world, these are formed over a million years ago. Highest Range Mountains are folded mountains. These mountains are formed when two plates collide head-on, mountains are formed just like when the paper is pushed together. Upward mountain is called anticlines, downward mountains are called synclines. Examples: the Himalayan Mountains, the Alps Mountains in Europe, the Andes in South America, the Rockies in North America, Urals in Russia. When the Indian plate is collided with the Asian plate, the Himalayan Mountains are formed.
• Fault-block Mountains: These mountains form when faults or rocks in the earth's crust. This faulting is caused by tension or compression, forces which lengthen or shorten the earth’s crust, causing section of it to subside or rise above. Examples: Sierra Nevada mountains in North America, Harz mountains in Germany
• Dome Mountains: Dome Mountains are the result of huge magma-molten rock that has reached on top of the earth’s crust. Without erupting, magma has pushed up all the layers reached the surface of the earth and then cooled down. The uplifted area which will be formed with this process is called Dome Mountains. Since the dome is above the surface of the earth, erosion happens from the top of the dome which results in a circular shape
• Volcanic Mountains: As the name suggests, these mountains are formed due to the volcanoes. These Mountains form when magma-molten rock erupts through the crust and piles upon on top of the surface. Magma is called lava when it breaks through the earth’s crust. Examples: Mt. St. Helens in North America, Mount Pinatubo in the Philippines, and Mt Kea and Mt Loa in Hawaii. Plateau Mountains- Erosion Mountains: Plateau mountains are not formed due to internal activity, these are formed due to erosion. Plateaus are large flat areas which are pushed above sea level by the forces within the earth or have been formed by the Lava. Examples: Mountains of New Zealand. 

4. Types of Plateaus

Plateaus are elevated uplands with extensive level surfaces and usually descend steeply into the surrounding lowlands. These are also termed as Tablelands. Like any other highlands or plateaus, they are subject to erosion which changes their original characteristics According to the mode of formation they are divided into three types, Tectonic plateau, Dissected plateau and Volcanic plateau. 

• Tectonic Plateau: These are caused by the earth’s movement resulting in the uplifting of plateaus and are normally of a considerable size with uniform altitude Examples: Deccan plateau. When plateaus are enclosed with Mountain ranges, they are called Innermost plateaus. Innermost plateaus are some of the highest and extensive plateaus in the world Examples: Tibetan plateau, Kunlun, Bolivian,
• Dissected plateaus: Through the continental process of weathering and erosion by running water, ice and winds, high extensive plateaus are gradually worn down and their surfaces are made irregular in the humid highlands stream action and sometimes glaciers cut deep narrow valleys in the plateau which are called dissected plateaus.  In drier countries, vertical corrosion by rivers and abrasion by winds dissect the plateaus into steep-sided tabular masses termed mesas and butter intersected by deep canyons. It’s a very common feature in arid and semi-arid areas.
• Volcanic plateaus: These are formed when magma erupts onto the surface of the earth’s crust. It spreads on the surface to form successive sheets of lava; these sheets solidify to become Volcanic (Lava) plateaus. Examples: Antrim plateau of Northern Ireland, the Northwestern plateau of the Deccan Plateau.  Deccan plateau is a peninsular plateau in central India which includes inland sections of Andhra Pradesh, Maharashtra and Karnataka.  Deccan Plateau is delineated by the Western Ghats and Nilgiri hills on the South. Eastern Ghats and Aravalli mountains in the North. The southernmost part of the plateau is drained by the Kaveri River. 

5. Types of Plains

• Structural plains: These are formed by Horizontal bedded rocks, relatively undisturbed by the crustal movements of the earth. EX: The Southeastern Plain of the USA was formed by the uplift of part of Mexico. 
• Erosional Plains: These kinds of plains are formed by the erosional elements like rivers, glaciation, wind, weathering etc. Ex: Canadian Shield and the West Siberian Plain. 
• Depositional Plains: These plains are formed with all the depositional sediments which are brought by rivers, glaciers and winds. Ex: Indo Gangetic plain