Rocks Rock makes up the solid part of the earth. Rock is made from minerals or rock can be made of solid organic matter. Three classes of rock: Igneous, Sedimentary, and Metamorphic. Any of the three types of rock can be changed into another of the three types or rock

Bowen’s Reaction Series In igneous rock, different minerals crystallize and solidify out of the magma at different temperatures. So different minerals form at different temperatures. The Bowen’s Reaction series represents the order that minerals crystallize as magma cools. The Bowen’s Reaction series is based on the minerals composition and melting point.

Felsic – light colored; Mafic – dark colored.

The Formation of Magma Magma forms as rock melts. Influenced by temperature, pressure, and presence of fluids (usually water) in the rock. Different minerals melt at different temperatures – The magma’s composition changes as it becomes hotter and more minerals are added to it as they melt. – As magma cools, the reverse happens as minerals crystallize.

Igneous Rock Textures Intrusive – cools deep inside crust from magma; – Coarse grained texture – slowly cools and hardens – Example: Granite Extrusive – cools on surface from lava; – Fine grained texture – rapidly cools and hardens – Examples: Basalt or Rhyolite Both Intrusive and Extrusive – Porphyritic texture – both coarse and fine grained; starts cooling inside crust and finishes cooling and hardening on surface. Others – Glassy texture – very fast cooling on surface. Example: Obsidian – Vesicular texture (holes) – rapidly cooling, traps gases as it hardens. Example: Pumice

coarse-grained texture vesicular texture

Composition of Igneous Rocks Felsic Rock – High in silica – Light colored – Mostly potassium feldspar and quartz, but also contains plagioclase feldspar, biotite and muscovite mica. Mafic Rock – Rich in iron and magnesium; low in silica (ferromagnesium minerals) – Dark colored – Minerals include plagioclase feldspar and pyroxene, hornblende, olivine Intermediate Rock – Minerals: Plagioclase feldspar, hornblende, pyroxene, and biotite mica. – Lower proportions of silica than felsics but higher than mafics.

Sedimentary Rock Made up of combinations of sediments. Sediments are formed from the weathering and erosion of rock. Then the loose sediment is deposited. Two main processes convert loose sediment to sedimentary rock: – Compaction – squeezes sediments together – Cementation – sediments are “glued” together.

3 Main Classes of Sedimentary Rock Chemical Sedimentary Rock – Forms from minerals that were once dissolved in water. – Dissolved minerals precipitate out of water – Can be caused by evaporation = evaporites – Examples: halite, gypsum, some limestones

3 Main Classes of Sedimentary Rock Organic Sedimentary Rock – Forms from the remains of living things. – Coal (plants), some Limestones (corals, clams, oysters, plankton), Chalk

3 Main Classes of Sedimentary Rock Clastic Sedimentary Rock – Made up of preexisting rock fragments that are carried away from their source by water, wind, or ice, and left as deposits. – The individual fragments may become compacted and cemented into solid rock. – Grouped according to the size of the fragments: Rounded fragments = conglomerates Angular fragments = breccias – Sandstones – sand sized particles (coarse-grained) – Shale – clay sized particles, layered (fine-grained)

Clastic Sediments Sorting – currents of air or water can separate sediments according to size. Well sorted – same size Poorly sorted – different sizes Due to changes in the speed of the moving sediment as it get deposited.

Stratification Layering of sedimentary rock Stratification layers are called beds. Cross beds – slanted layers Graded beds – largest sediments on bottom smallest on top.

Ripple marks – evidence of shallow water or wind (beach or river bed) Mud cracks – form when mud dries and shrinks (flood plain, dry lake bed) Fossils – plants and animals get buried in sediments before it becomes rock. Concretions/Geodes – form when minerals precipitate out of fluids and build up around a nucleus.

Metamorphic Rocks Metamorphism occurs when heat, pressure, or chemical processes change one type of rock to another. Forms deep within Earth’s crust Changes the mineral composition of the rock

Two Main Types of Metamorphism Contact Metamorphism When magma comes into contact with existing rock, heat from the magma can change the structure and mineral composition of the surrounding rock. Regional Metamorphism Occurs when large areas of rock undergo metamorphism. Brought on by tectonic activity.

Classification of Metamorphic Rocks Foliated Rock Minerals are arranged in planes or bands. Extreme pressure may cause the mineral crystals to realign or regrow to form parallel bands. May alternate between light and dark bands. Slate, shist, gneiss Non-Foliated Rock Do not have bands or aligned minerals. Quartzite forms from sandstone Marble forms from limestone

Foliation