Sci Chp 7 #4: Igneous Rocks Definition, Types & Examples

Which statement best describes a porphyritic texture?

• A porphyritic texture is characterized by large crystals (phenocrysts) surrounded by a fine-grained matrix (groundmass).
• A porphyritic texture is characterized by a uniform crystal size throughout
• A porphyritic texture is formed by rapid cooling of molten rock
• A porphyritic texture consists of only fine-grained crystals

Which best describes Felsic rocks?

• Igneous rocks low in silica and high in iron
• Metamorphic rocks with high quartz content
• Sedimentary rocks rich in iron and magnesium minerals
• Igneous rocks that are light in color and contain a large amount of feldspar and quartz

Which statement best describes Mafic Rocks?

• Dark-colored, dense, rich in iron and magnesium minerals
• Dark-colored, lightweight, rich in silicon and aluminum minerals
• Medium-colored, dense, rich in calcium and potassium minerals
• Light-colored, porous, rich in iron and magnesium minerals

Which statement best describes Ultramafic rock

• Ultramafic rocks are sedimentary rocks with high silica content.
• Ultramafic rocks are metamorphic rocks with low magnesium and iron levels.
• Ultramafic rocks are extrusive rocks formed from rapid cooling of lava.
• Ultramafic range from black to olive green and are made of mainly magnesium and iron with very little silica (less than 45%)

What are the three types of igneous rock?

• volcanic, magnetic, igneous

• metamorphic, extrusive, granite

• sedimentary, volcanic, intrusive

• felsic, mafic, ultramafic