How are rocks formed by volcanic eruptions?

Volcanologists look for these igneous rocks so that they can learn more about where these rocks have come from and whether they were formed during a volcanic eruption. read more

Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. read more

Lava solidifies to rock. New Zealand has 3 main types of volcanoes, and each has been formed from a different type of magma. Once the lava has erupted, it cools and solidifies into rock: Basalt magma often forms shield volcanoes. Andesite magma often forms cone volcanoes. Rhyolite magma often forms calderas. read more

Magma that is ejected during a volcanic eruption forms extrusiveigneous rocks. They are also referred to as volcanic rocks. read more

Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from magma erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. read more

They are large volcanic craters that form by two different methods: 1) an explosive volcanic eruption; or, 2) collapse of surface rock into an empty magma chamber. The accompanying image is a satellite view of one of the most famous calderas - Crater Lake in Oregon. read more