Maharashtra State Board
Standard VI – Geography
Chapter 7 – Rocks and Rock Types
(A) How is sand that flows in a river formed? Collect some information about where the sand comes from.
Ans: Rivers mainly originate in the mountains. As a river flows, it carries rocks and soil particles along with it. Due to the fast flow of water, these rocks collide with each other and with the river bed.
Because of this continuous friction, the rocks break into smaller pieces. Over time, these pieces become very fine particles. The flowing river carries these small particles to lower areas and deposits them there. These deposited particles form sand.
Thus, river sand mainly comes from the breaking down of rocks in the mountains.
(B) Which of the following monuments are built in igneous rock?
(1) The Taj Mahal
(2) Fort Raigad
(3) The Red Fort
(4) Ellora Sculpture
Ans: Ellora Sculpture
Explanation: Igneous rocks are formed when molten rock (magma or lava) cools and solidifies. The Ellora Sculptures in Maharashtra are carved from basalt rock. Basalt is an igneous rock formed due to volcanic eruptions. Therefore, the Ellora Sculptures are built in igneous rock.
(C) Find the differences between –
(1) Igneous and Sedimentary Rocks
| Sr. No. | Igneous Rocks | Sedimentary Rocks |
|---|---|---|
| 1 | Igneous rocks are formed when molten material called magma (inside the Earth) or lava (on the surface) cools and solidifies. | Sedimentary rocks are formed when small rock particles are deposited in layers and become hard over a long period of time. |
| 2 | Igneous rocks are hard, heavy, and uniform in structure. | Sedimentary rocks are generally soft, brittle, and light in weight. |
| 3 | Examples: Basalt, Granite, Pumice. | Examples: Sandstone, Limestone, Conglomerate. |
(2) Sedimentary and Metamorphic Rocks
| Sr. No. | Sedimentary Rocks | Metamorphic Rocks |
|---|---|---|
| 1 | Sedimentary rocks are formed from layers of sediments that become hard over time. | Metamorphic rocks are formed when existing rocks change due to heat and pressure. |
| 2 | They are generally soft and brittle. | They are hard and compact. |
| 3 | Examples: Sandstone, Limestone. | Examples: Marble, Slate, Quartzite. |
(3) Igneous and Metamorphic Rocks
| Sr. No. | Igneous Rocks | Metamorphic Rocks |
|---|---|---|
| 1 | Igneous rocks are formed by the cooling and solidification of magma or lava. | Metamorphic rocks are formed when existing rocks change due to heat and pressure. |
| 2 | They are hard and uniform in structure. | They are hard and may show layers or bands due to changes. |
| 3 | Examples: Basalt, Granite. | Examples: Marble, Slate. |
(D) Which types of rocks are predominantly found at the following locations?
(1) Central Maharashtra
Ans: Basalt rock is predominantly found in Central Maharashtra.
(2) South Konkan
Ans: Granite and laterite rocks are predominantly found in South Konkan.
(3) Vidarbha
Ans: Granite, basalt, and sedimentary rocks are predominantly found in Vidarbha.