magmakiviä

Magmakiviä, also known as igneous rocks, are one of the three main rock types, alongside sedimentary and metamorphic rocks. They are formed through the cooling and solidification of molten rock material. This molten material can originate either from deep within the Earth's mantle, where it exists as magma, or from volcanic eruptions, where it is called lava.

The process of magma or lava cooling and hardening is called crystallization. The texture and mineral composition of magmakivi depend heavily on the rate of cooling and the chemical composition of the original molten material. Rapid cooling, such as that of lava erupting onto the Earth's surface, often results in fine-grained or even glassy rocks, where individual crystals are too small to be seen with the naked eye. Examples include basalt and obsidian. Slow cooling, which occurs when magma solidifies beneath the Earth's surface, allows for larger crystals to form, resulting in coarse-grained rocks like granite and gabbro.

Magmakivi are broadly classified into two main categories based on their origin: intrusive (or plutonic) rocks and extrusive (or volcanic) rocks. Intrusive rocks form when magma cools and solidifies slowly beneath the Earth's surface. Extrusive rocks, on the other hand, form when lava cools and solidifies on the Earth's surface. These rocks are a fundamental part of the Earth's crust and play a significant role in geological processes and landform creation.