GEOLOGY

Detailed explanation-1: -The top 20–25 km of the Earth’s crust consists of approximately 95% igneous rocks or their metamorphic equivalents, 4% shale, 0.75% sandstone, and 0.25% limestone. The average chemical composition of common rocks is given in Table 1.

Detailed explanation-2: -Chemical analyses of the most abundant components in rocks usually are presented as oxides of the elements; igneous rocks typically consist of approximately 12 major oxides totaling over 99 percent of the rock. Of the oxides, silica (SiO2) is usually the most abundant.

Detailed explanation-3: -Sedimentary rocks are rocks that are made from pieces of other rocks. They are the most common type of rock that covers the Earth’s surface, with approximately 75% of the rocks at the Earth’s surface being sedimentary.

Detailed explanation-4: -Detailed Solution. The correct answer is Basalt.