ROCKS

IGNEOUS ROCKS

• Formed by cooled lava or magma
• There are coarse-grained and fine-grained igneous rocks
• Obsidian is a well known igneous rock

COARSE GRAIN ROCKS

• Petrologists may classify a coarse-grained igneous rock as a pegmatite, a porphyry, or a phanerite.
• Coarse grain igneous rocks contain large mineral grains
• Most of the rocks are intrusive

FINE GRAINED ROCKS

• Made from small mineral grains
• Rock families are basalt, andesite, and rhyolite
• Geologist believe extrusive volcanism produces fine grain rocks

SEDIMENTARY ROCKS

• Are formed in various steps
• Erosion and solution
• Transportation and deposition
• Compaction
• Cementation

METAMORPHIC ROCK

• Were formed from igneous, sedimentary, or even other metamorphic rocks that chemically and physically changed over time
• There are three types of metamorphic types
• Contact metamorphism
• Dynamic metamorphism
• Regional metamorphism

OLD EARTH ROCK CYCLE

• Believe that rock is recycled just like nearly every other natural resource
• They believe igneous rocks were the first to form billions of years ago as the earth’s crust cooled and hardened
• Then the sediments from eroded rocks ( formed over millions of years) gradually turn into sedimentary rocks after more time has passed
• The procedure is the steps of igneous rocks changing into sedimentary rocks
• Their rock cycle theory assumes that sedimentary rocks can become magma again

OLD EARTH ROCK CYCLE

• They also believe some rocks can get sidetracked and follow a different path
• Metamorphism is one of the paths all rocks can take in the old-earth rock cycle
• After metamorphism, the rocks can follow either to be eroded path or to be melted into magma path

YOUNG EARTH VIEW

• agree that certain parts of a hypothetical rock cycle seem to be happening today
• Earth’s history as understood by the young-earth view is much shorter than that of the old-earth theory
• There is not enough time for any atom within a rock to complete even a tiny fraction of one rock cycle, except under catastrophic conditions
• Young-earth geologists conclude that the earth was not originally designed to recycle rocky earth materials at all
• Most magma and volcanic lava today probably comes directly from the mantle or from deep in the crust

YOUNG EARTH VIEW