Rocks and rock cycle - class-VIII

• Marble is formed when limestone is subjected to intense heat and pressure leading to its metamorphism i.e. change in form. Hence marble is called a metamorphic rock

Igneous rocks are called as primary rocks because they originate during the formation of upper crust of the earth on cooling, solidification and crystallization of hot and liquid magmas after the origin of the earth. 

Limestone, Sandstone, and Shale are examples of sedimentary rocks but Marble is an example of metamorphic rock. 

Magma is the term for molten rock located beneath the Earth's surface. Once it reaches the surface through volcanic activity, it is referred to as lava.

• Igneous rocks are the rocks that are formed by the cooling of hot masses or by the solidification of molten matter, hence option B is correct.
• Hard rock is any rock that is hard. It is a very general term.
• Aqueous rocks are the rocks deposited by the water and they get formed in layers or strata.
• Volcanic rocks are the rocks coming out of the volcanic eruption which are mostly of igneous origin but as already the specific option of Igneous rocks is provided, option D is not the most suitable answer.

• When any rock gets broken it eventually gets eroded and transported to a different place where it settles down in layers. When many layers of such broken materials are piled up and take the form of a rock then it is called a sedimentary rock, hence option A is correct.
• Soft rock is a general term for any soft rock.
• Organic rock is a sedimentary rock which has high organic carbon.

• Marble, Slate and quartz are formed after metamorphism ie change in their original form due to extreme temperatures and pressure.
• Granite is an igneous rock, thus option B is correct.

Igneous rocks are formed during the formation of the upper crust of the earth on cooling, solidification, and crystallization of hot and liquid magmas after the origin of the earth. Igneous rocks are mostly associated with the volcanic activities and igneous rocks are generally found in the volcanic zones.

None of the above

• Permeable rocks are the rocks having interconnected pores which allow the water to seep through them. Hence option A is correct.
• Sedimentary rocks and metamorphic rocks are a  broad classification of rocks.
• Mushroom rocks derive their name out of their shape.

• When the lava solidifies before reaching the surface, it gives rise to the rocks called plutonic rocks.
• Volcanic rocks are formed when lava solidifies on the surface of the earth.
• Sedimentary and metamorphic rocks are not directly related to lava.
• Hence option B is the correct answer.

Stalactites and stalagmites are the depositional landforms of limestone areas. The calcareous deposits from dripping of water in dry caves are called dripstones. The columns of dripstones hanging from the cave ceiling are called stalactites while the calcareous columns of dripstones growing upward from the cave floor are known as stalagmites.

Igneous rocks begin the rock cycle, and are therefore called primary rocks. Two major divisions include- volcanic or extrusive rocks that form when magma is ejected from the Earth's crust, and intrusive rocks, which are created below the surface.

Marble is a metamorphic rock formed from the metamorphism of limestone or dolomite. The heat and pressure cause the calcite in the limestone to recrystallize.

Precious stones like rubies, emeralds, and sapphires are typically found in metamorphic rocks, which form under high pressure and temperature conditions that allow for the growth of these crystals.

The rocks having a broad upper part and narrow base resembling an umbrella or mushroom are called mushroom rocks. Mushroom rocks are curved by the erosional work of winds. 

• Granite rock is formed from the cooling of lava so it is found as an igneous rock. Hence option A is correct.
  
• Rest options are of different category of rocks.

Quartzite is a metamorphic rock that is formed by interlocking quartz grains from quartz sandstone. The rock is hard rock, nonfoliated.

Granite is a light-colored igneous rock. It is composed mainly of quartz and feldspar with a little amount of mica, amphiboles and other minerals. Granite is the world's toughest substance and is used in jewelry making. As few granites are rare and extremely beautiful. They are used as gemstones. Example of granite- blue tint found in the Himalayas etc.

The process of transformation of existing rocks is known to be metamorphism.

Basalt is formed when lava cools on the earth's surface.
Granite is formed when magma cools below the surface of earth.
Pumice is formed by cooling of froth lava on the surface.

Marble is formed from the sedimentary rocks. It is also used in making statues.

Feldspar, quartz and mica are the minerals present in granite.
Granite is formed when magma cools below the surface of earth.

Sandstone is a sedimentary rock composed primarily of sand-sized mineral particles or rock fragments, most commonly quartz, because quartz is highly resistant to weathering.

Metamorphic rocks are formed by the transformation of igneous or sedimentary rocks into different kinds of rocks under intense heat and pressure.
Marble is formed by metamorphosis of limestone.
Gneiss is formed by metamorphosis of granite.
Slate is dark grey shiny rock made by metamorphism of shale. Used to make slates and blackboards.

Pumice is a light volcanic rock. It has a lot of pores in it. It is an igneous rock. The rock is light enough to float on water until it becomes waterlogged. Pumice is a very light rock which is used as body scrubber and to polish floor.

The word 'igneous' is derived from a Latin word 'ignis' meaning fire. Igneous rocks are known as primary rocks as they are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.

• Generally, rocks can be divided into three major types based on the process of their formation
• Igneous rocks are formed by the solidification and cooling of magma in volcanic areas, 
• While sedimentary rocks are formed by a low-temperature accumulation of sediments in tectonic basins and topographical sinks. 
• Metamorphic rocks on the other hand are formed by application of temperature and pressure on pre-existing rocks