Intrusive igneous rock is formed when magma or lava cools quickly.
When lava cools quickly, the mineral grains don't have much time to set. This causes the rock to be light and porous.
pumice rocks are formed when a lava cools down quickly & comes out of volcano
How quickly it cools is one of the reasons
When magma cools quickly, small crystals, or in some cases, no crystals are formed in the resultant rock.
Volcanic/extrusive igneous rock.
It depends on how fast the lava cools after it is released from the volcano. If it cools quickly, it will become a porous rock, often with holes, such as pumice. If it cools slowly, it will form crystals and turn into a dense rock such as obsidian.
When a volcano erupts the molten cools quickly it is also known as volcano glass
Basalt cools off quickly because it is formed under water.
Pumice, an extrusive igneous rock. Pumice is very porous and therefore allows air to get trapped when it is in water. Pumice stones are formed when lava cools quickly, they are usually white in colour and have a heavily pitted surface.
Pumice is an igneous rock that forms when magma traps gas bubbles and cools quickly. The gas dissipates and leaves the distinctive porous nature of the pumice
Obsidian is formed as extruded lava with a high silicon content that cools quickly. So the environment would be a volcano.
Igneous rocks range from the highly porous pumice to the nearly non-porous granite. In some explosive eruptions of felsic magma, as is the case with pumice, the frothy mixture of rock and gas cools so rapidly that open vesicles are preserved, making it very lightweight and porous. With granite, the intrusive igneous rock has had a long time to cool underground, and with its interlocking crystalline structure, it has an extremely low porosity.
Fine-grained igneous rocks form when the magma cools quickly.
Granite forms when magma cools slowly underground and forms relatively large crystals. Pumice forms when gas-rich lava is ejected into the air by a volcano and cools quickly to form porous glass with no crystals.
The individual grains (crystals) in quickly cooled magma are described as aphanitic--not visible without magnification.
When a magma cools/solidifies, crystals are formed. The quicker the magma cools, the tinier the crystals. A granite for example, which is formed through slow cooling in the Earth's crust, consists out of big crystals. Contrary, magma erupting at the surface (which is then called lava) cools rapidly and consists out of tiny crystals. In extreme cases, the lava cools so rapidly that the resulting rock appears glassy. Hope this helps!
igneous rock is formed when lava cools down
If it cools faster, smaller crystals are formed. If it cools for longer, larger crystals are formed.
Lava that cools quickly forms extrusive igneous rock.
Pumice is an igneous rock. Pumice is formed by hot lava filled with gas cools quickly and forms.
Magma that cools quickly forms into igneous rock, when it cools quickly it becomes a lava rock. Lava cools very quickly at first and forms a thin crust that insulates the interior of the lava flow.
A rock that is formed when magma cools is called a igneous rock.