Rocks Rock Origin Igneous Rocks Formed from the

Rocks

Rock Origin • Igneous Rocks - Formed from the cooling of molten magma or lava. • Sedimentary Rocks- Formed from particles of other rocks or remains of plants and animals that are cemented together in layers. • Metamorphic- Formed when an existing rock is changed by extreme heat and pressure, usually takes place deep under ground.

• Aim: How do igneous rocks form?

Igneous rocks • All have crystals. • All result from magma or lava • Origin – Extrusive Igneous rock • Formed from lava eruption, which means it formed on earth’s surface. – Intrusive Igneous rock • Igneous rock formed when magma hardened beneath earths surface.

Igneous rock cont. • Texture – Depends on mineral crystals. • Rapid cool = fine grained (Small Crystals) • Slow cool = coarse grained (Large Crystals) • Porphyritic = cools slow then fast (both small and large crystals) • Intrusive rocks have larger crystals than extrusive. • Mineral composition – See reference table pg 6 • Uses of igneous rock – Building = Cobblestone, Curbs, stone Statues, Huge Ancient Structures.

Igneous rock formation

Sedimentary Rocks • Sediments that come from rock and living things are deposited in layers and become sedimentary rock. Formation • Erosion = Water and Wind loosening and carrying away fragments of rock. • Deposition = settling of sediments. – Pieces of shells, bones, leaves and so forth can also be deposited. • Compaction = pushing sediments together. • Cementation = minerals crystallize in the spaces between sediments and cement the sediments together.

Sedimentary Rock Formation

Types of Sedimentary Rocks • Classified by the types of sediments • Clastic rocks – Formed from broken pieces of other rocks. – Examples • Shale = clay particles • Sandstone = sand • Conglomerate = large pebbles • Organic rocks (bioclastic) – Formed from the remains of substance that were once living – Examples • Coal = Remains of swamp plants buried in water • Limestone = Hard shells glued together.

Types of Sedimentary Rocks • Chemical Rocks – Formed when mineral dissolved in solution and crystallize. – Examples • Gypsum = from evaporation • Limestone = From dissolved calcite ( different than organic) Use of sedimentary rocks • Used in building supplies because of ease to cut and shape ( White House is sandstone).

Metamorphic • Heat and Pressure deep beneath the earth’s surface can change any rock to metamorphic rock. • The change results in a different appearance texture, crystal structure, and mineral content. Classifying • Done by looking at grain arrangement. – Arranged in bands = foliated ex. slate – Random arrangement = Nonfoliated rock ex. marble

Metamorphic Rock Formation

The Rock Cycle • is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly.

Interactive Rock Cycle Animation