1. three kinds of rocks
1.1. igneous
1.1.1. formation
1.1.1.1. they are formed by solidification of lava
1.1.2. characteristics
1.1.2.1. they are hard
1.1.2.2. all igneous rocks are crystalline
1.1.2.3. size depends upon the rate of cooling
1.1.2.4. they do not have layers and do not contain fossils
1.1.2.5. they are not easily weathered
1.1.3. examples
1.1.3.1. granite
1.1.3.2. basalt
1.1.3.3. pumice
1.2. sedimentary
1.2.1. formation
1.2.1.1. they are formed through the consolidation of sediments
1.2.2. characteristics
1.2.2.1. they are found in layers
1.2.2.2. most of the rocks contains fossils
1.2.2.3. they are porous
1.2.2.4. they are not crystalline
1.2.2.5. they are prone to weathring
1.2.3. examples
1.2.3.1. sandstone
1.2.3.2. limestone
1.2.3.3. shale
1.3. metamorphic
1.3.1. formation
1.3.1.1. they formed by the process of metamorphism (alteration or transformation)
1.3.2. characteristics
1.3.2.1. they are very hard
1.3.2.2. they have a banded structure
1.3.2.3. when igneous rocks and sedimentary rocks go under high pressure, they form metamorphic rocks
1.3.2.4. it takes a long time for them to form
1.3.3. example
1.3.3.1. marble
1.3.3.2. hornfels
1.3.3.3. slate
2. rock cycle
2.1. the transformation of one rock to another is called the rock cycle
2.2. internal process
2.2.1. the internal movement of tectonic plates
2.3. external process
2.3.1. takes place on the surface of the earth
3. weathering
3.1. it is the breaking down of rocks by the agents present in the atmosphere
3.2. kinds of weathering
3.2.1. physical weathering
3.2.1.1. two factors of physical weathering
3.2.1.1.1. temperature
3.2.1.1.2. frost
3.2.2. chemical weathering
3.2.2.1. the decomposition of rocks due to chemical reactions
3.2.3. biological weathring
3.2.3.1. trees may grow from the rocks
4. soil
4.1. the thin upper layer of the earth's surface
4.2. vital part of the natural environment
4.3. soil conservation
4.3.1. afforestation
4.3.2. restricted grazing
4.3.3. constructing dams
4.3.4. proper farming techniques
4.3.4.1. crop rotation
4.3.4.2. checking of shifting agriculture
4.3.4.3. terracing
4.3.4.4. ploughing
4.3.4.5. soil erosion