EVERYDAY SCIENCE

Detailed explanation-1: -Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface. These are the rocks that form at erupting volcanoes and oozing fissures.

Detailed explanation-2: -The rock beneath the Earth’s surface is sometimes heated to high enough temperatures that it melts to create magma. Different magmas have different composition and contain whatever elements were in the rock that melted.

Detailed explanation-3: -Minerals form when magma and lava cool. Some minerals crystallize at hotter temperatures. These minerals form first. Other minerals form at cooler temperatures.

Detailed explanation-4: -The minerals present will be olivine, pyroxene, and calcium-rich plagioclase. If the magma cools slowly underground, the product will be gabbro; if it cools quickly at the surface, the product will be basalt (Figure 3.13).

Detailed explanation-5: -As a magma cools below 1300°C, minerals start to crystallize within it. If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture.