1. Igneous Rocks:
* Formation: Formed from the cooling and solidification of molten rock (magma or lava).
* Process:
* Magma: Molten rock beneath the Earth's surface. When it cools and solidifies, it forms intrusive igneous rocks (e.g., granite).
* Lava: Molten rock that has erupted onto the Earth's surface. When it cools and solidifies, it forms extrusive igneous rocks (e.g., basalt).
* Key Characteristics: Often have a crystalline texture, can be fine-grained (rapid cooling) or coarse-grained (slow cooling).
2. Sedimentary Rocks:
* Formation: Formed from the accumulation and cementation of sediments (fragments of other rocks, minerals, or organic materials).
* Process:
* Weathering and Erosion: Existing rocks are broken down into smaller pieces by wind, water, ice, or chemical reactions.
* Transportation: Sediments are transported by wind, water, or ice to a new location.
* Deposition: Sediments settle and accumulate in layers.
* Compaction and Cementation: Over time, the weight of overlying sediments compacts the layers and dissolved minerals in groundwater act as a cement, binding the sediments together.
* Key Characteristics: Often layered or stratified, may contain fossils, can be clastic (made of fragments) or chemical (precipitated from water).
3. Metamorphic Rocks:
* Formation: Formed when existing igneous, sedimentary, or even other metamorphic rocks are transformed by heat and pressure (without melting completely).
* Process:
* Heat: Increases the mobility of atoms within the rock, allowing minerals to recrystallize.
* Pressure: Compresses the rock, causing minerals to align and form a layered texture.
* Chemical Reactions: The heat and pressure can also cause chemical reactions to occur, changing the mineral composition of the rock.
* Key Characteristics: Often have a foliated texture (layered), can be recrystallized and have a different texture than their parent rock, may contain unique minerals formed during metamorphism.
A Simple Analogy:
Think of baking a cake:
* Igneous rock: The batter (magma) is poured into the pan (Earth's crust) and bakes (cools and solidifies) into a cake (igneous rock).
* Sedimentary rock: Cake crumbs (sediments) are collected, mixed with frosting (cement), and pressed together (compacted) to form a new cake (sedimentary rock).
* Metamorphic rock: The baked cake (existing rock) is subjected to heat and pressure (oven) and changes texture and color (metamorphic rock).
