Magmakivi

Magmakivi, also known as igneous rock, is a type of rock formed from the cooling and solidification of molten rock material. This molten material can exist as magma, which is found beneath the Earth's surface, or lava, which is molten rock that has erupted onto the surface. The process of cooling and solidification is called crystallization.

There are two main categories of magmatic rocks based on where they cool. Intrusive, or plutonic, igneous rocks form when magma cools and solidifies slowly beneath the Earth's surface. This slow cooling allows for the formation of larger mineral crystals, giving these rocks a coarse-grained texture. Examples include granite and gabbro.

Extrusive, or volcanic, igneous rocks form when lava cools and solidifies rapidly on the Earth's surface. The fast cooling results in smaller mineral crystals, leading to a fine-grained texture. In some cases, cooling can be so rapid that no crystals form, creating volcanic glass like obsidian. Other examples include basalt and rhyolite.

The composition of magmatic rocks varies depending on the chemical makeup of the original magma or lava. This composition influences the types of minerals present and the overall color and properties of the rock. Magmatic rocks are fundamental to understanding the Earth's crust and its geological history.