Rock formed from originally molten material (magma), can be either plutonic (cooling far below the earthâ€(tm)s surface) or volcanic (cooling on or near the earthâ€(tm)s surface). Minerals from these rocks often are used for calculating radiometric ages.
Igneous rock are formed from magma (melted rock) that has cooled and solidified, either within the Earth's crust or on the Earth's surface. Magma that solidify within the Earth's crust cools slowly and result in coarse-grained (large crystal) rock; for example, granite. Magma that solidify at or near the Earth's surface cools rapidly and result in fine-grained (small or no crystal) rock; for example, basalt and obsidian. Igneous rock is composed of mostly silicate minerals
created when melted rock, called magma, gets trapped in pockets deep inside the Earth. When the magma cools and hardens it is known as igneous rock. Igneous rock is also formed when lava from volcanoes cools and hardens. Lava is just magma that is no longer underground, but has come out through a volcano. Granite is an example of igneous rock. Igneous rock is very hard so water does not break it up very easily. That is why low salinity is associated with an igneous ocean floor.
When molten rock (lava) cools, igneous rock is formed. Jurassic Period A geological period of the Mesozoic Era, between about 200 and 135 million years ago. Dinosaurs flourished during this time. Kingdom The highest group of like-organisms in scientific classification. Dinosaurs are part of the Animal Kingdom.
When molten rock cools, igneous rock is formed. INDEX FOSSILS Index fossils are commonly found fossils that are limited in time span. They help in dating other fossils. For example: trilobites were common during the Paleozoic, but not found before the Permian period, and ammonites were common during the Mesozoic Era, but not found after the Cretaceous period.
When molten rock cools, igneous rock is formed. Intrusive rocks are igneous rocks that have formed (and cooled slowly) beneath the surface of the Earth. Extrusive rocks are igneous rocks that have formed (and cooled more quickly) at the surface of the Earth (like obsidian). Some igneous rocks include granite, obsidian (volcanic glass), basalt, and andesite porphyry.
One of the three principal types of rock, along with sedimentary and metamorphic rock. Igneous rock is formed by the crystallization of molten materials, for instance, in a volcano or other setting where plate tectonicprocesses take place.
Igneous rocks are formed when rock (magma) cools and solidifies, with or without crystallisation, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either the Earth's mantle or crust. Typically, the melting is caused by one or more of the following processes -- an increase in temperature, a decrease in pressure, or a change in composition.