(1) What are igneous rock ? …

Igneous rocks are formed from the solidification of molten rock material. ... Examples of intrusive igneous rocks are diabase, diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Igneous rocks (from the Latin word for fire) form when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust. All magma develops underground, in the lower crust or upper mantle, because of the intense heat there. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool.

Rocks that formed from magma are called igneous rocks. Igneous comes from the Latin word ignis which means "fire". Rocks that are formed from heat and pressure are called metamorphic rocks. Rocks that are formed from the cementing together of small pieces of rocks or shells are called sedimentary rocks. Igneous — they form from the cooling of magma deep inside the earth. Metamorphic — they are formed through the change (metamorphosis) of igneous and sedimentary rocks. They can form both underground and at the surface. Sedimentary — they are formed through the solidification of sediment.