Rock Formed from Lava (Extrusive Igneous Rock)
* Cooling rate: Rapid cooling. Lava is exposed to the air and water, which cools it much faster than magma deep underground.
* Crystal size: Small crystals (fine-grained). The rapid cooling doesn't allow for large crystals to form.
* Texture: Aphanitic (fine-grained, crystals are too small to see without magnification).
* Examples: Basalt, rhyolite, andesite.
Magma Deep in the Crust (Intrusive Igneous Rock)
* Cooling rate: Slow cooling. Magma is insulated by surrounding rock, leading to a gradual cooling process.
* Crystal size: Large crystals (coarse-grained). The slow cooling allows time for large crystals to form.
* Texture: Phaneritic (coarse-grained, crystals are easily visible).
* Examples: Granite, gabbro, diorite.
Key Differences:
* Crystal Size: The primary difference is the crystal size. Lava cools quickly, resulting in small, fine-grained crystals. Magma cools slowly, producing large, coarse-grained crystals.
* Texture: The texture of the rock reflects the crystal size. Extrusive rocks have an aphanitic texture (fine-grained), while intrusive rocks have a phaneritic texture (coarse-grained).
* Mineral Composition: While the cooling rate influences crystal size and texture, the chemical composition of the magma/lava also determines the minerals present in the final rock.
Let's consider an analogy:
Imagine baking a cake. If you bake it at a high temperature for a short time, the batter will cook quickly, and the cake will have a fine crumb (like extrusive rocks). If you bake it at a low temperature for a long time, the batter will cook slowly, and the cake will have a coarse crumb (like intrusive rocks).
In Summary:
The differences between rocks formed from lava and magma are largely due to the rate of cooling. This affects the size of the crystals formed and the overall texture of the resulting rock.
