Classification based upon formation

Igneous rocks form from molten lava.

What’s the difference between magma and lava?

The formation of igneous rocks is destructive because old rocks are melted

and constructive because new rocks are formed.

IGNEOUS ROCKS

When magma cools slowly while still under ground, the minerals in the rock have time to form crystals.

Those crystals make intrusive igneous rocks have a coarse grain with visibly mottled coloration.

IGNEOUS ROCKS

Granite is a coarse grained intrusive rock made mostly of quartz

OTHER INTRUSIVE IGNEOUS ROCKS

Peridotite is a coarse-grained igneous rock made mostly of olivine

Diorite is a coarse grained igneous rock made mostlyof feldspar

When lava cools on the Earth’s surface, there is little time for crystals to form, so extrusive igneous rocks lack the coarse grain typical of intrusive igneous rocks.

EXTRUSIVE IGNEOUS ROCKS

Basalt is a fine-grained extrusive igneous rock, which happens to bethe most common rock on Earth. It is susceptible to chemical weathering, where it breaks down to form clay.

Obsidian is volcanic glass which cools so rapidly that not even the finest crystals can form.

EXTRUSIVE IGNEOUS ROCKS

EXTRUSIVE IGNEOUS ROCKS

Pumice cools so quickly and with so many gas bubbles that it can float.

Scoria is another igneous rock filled with vesicles – the proper term for the gas bubbles in these rocks.

Metamorphic rocks have been modified by heat, pressure and chemical process usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture and chemical composition of the rocks.

METAMORPHIC ROCKS

Marble is an nonfoliated metamorphic rock which forms when limestone is exposed to great heat and pressure.

METAMORPHIC ROCKS

Both slate (below) and gneiss (at right)are examples of foliated metamorphic rocks .

Foliated metamorphic rocks have obvious layers and often split into thin sheets.

Sedimentary rocks form from the accumulation of sediments, often but not always at the bottom of a body of water.Sedimentary rocks are divided into three major groups: clastic, chemical, and organic.

SEDIMENTARY ROCKS

Conglomerate is a clastic sedimentary rock, which means it forms as a result of mechanicalweathering.

CLASTIC SEDIMENTARY ROCKS

Sandstone and shale are both clastic sedimentary rocks. Sandstone is made of compressed particles of sand, and shale is made of smaller particles of clay or mud.

CHEMICAL SEDIMENTARY

Halite is rock salt which forms when bodies of salt water evaporate, leavingtheir salt content behind.

Hematite is iron ore that formed when the iron and oxygen in bodies of water chemically reacted and settled to the sea floor.

ORGANIC SEDIMENTARY ROCKS

Coal forms from the remains of decayedplant matter in swampy environments.

Limestone forms from the accumulation ofcalcium-rich shells, coral and other detritus of marine life

In what ways is the formation of sedimentary rocks both constructive and destructive?

How is the water cycle vital to the formation of sedimentary rocks?

SEDIMENTARY ROCKS