Soft Rock and Hard Rock
The Earth's crust contains elements (oxygen, iron, calcium, silicon, etc.) These elements combine in different ways to make minerals. Rocks are made of minerals.
Soft Rocks
Nepean sandstone, a sedimentary rock
Source
Sedimentary rocks-- "deposited rocks"
Sedimentary rock is formed when particles of eroded rock called sediment (such as sand, silt, mud and clay) are carried by water, ice or wind. Sediment piles up, along with plant and animal remains. Over millions of years, the weight of the layers presses down on the lower layers, squeezing and cementing them together to form rock.
Hard Rocks
Garnet gneiss, a metamorphic rock
Source
Metamorphic rocks -- "changed rocks"
Metamorphic rocks are sedimentary, igneous or old metamorphic rocks that have changed shape and composition due to changes in pressure, heat (though not melted) and chemical conditions below the Earth's surface.
Feldspar porphyry, an intrusive igneous rock
Source
Igneous rocks -- "liquid rocks"
Igneous rocks are made of molten magma that has cooled. Magma usually comes from the semi-fluid mantle below the Earth's crust and sometimes from re-melted rocks in the crust. As the magma rises from deep in the Earth, it cools and solidifies, either below ground or above, such as when a volcano erupts.
