Rocks

• FORMATION OF ROCKS

  Tracing the birth, formation, and transformation of rocks will take us two sets of physical processes.

  • ENDOGENIC PROCESSES - refer to geologic processes that take place below the Earth's surface, the interior of the planet.
  • EXOGENIC PROCESSES - refer to those that take place on the Earth's surface.
• Earth, as a terrestrial planet is composed of rocks and minerals

  in one of its subsystem called lithosphere.
• LITHOSPHERE

  i s solid and it is the outermost layer of our planet.
• Rocks are solid materials consisting of one or more minerals. They form the Earth's outer layer, known as the crust. Different colors, shapes, and sizes characterize them.

  There are three major types of rocks based on their characteristics.

  ROCKS

  is a naturally occurring aggregate of minerals and a certain non-mineral material such as fossils and glass.
• igneous rock forms when molten magma cools and hardens into solid rock. This can happen either beneath the earth’s surface (intrusive) or above ground level (extrusive).
• Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.
• 3 Types of Rock: Igneous, Sedimentary & Metamorphic 
• EXTRUSIVE IGNEOUS ROCK

  magma erupts at the Earth's surface and solidifies upon

  contact with the atmosphere or ocean.
• VOLCANIC ROCKS When lava is exposed to the to

  bodies of atmosphere

  or water, they rapidly cool down and turn to rocks.
• VOLCANIC ROCKS contain only small crystals, and often display a glassy appearance.

  EXAMPLE: Pumice
• intrUSIvE IGNEOUS ROCK

  If magma solidifies underground.
• PLUTONIC ROCKS

  Pluto is the ancient Roman God of the underworld. His counterpart in Greek mythology is HADES.
• BATHOLITHS (PLUTONS)

  Are a huge mass of plutonic rocks hundreds of kilometers long and

  100 km wide. They form below the Earth's

  surface.
• sills are plutonic rocks that intruded into cracks and crevices of

  existing rocks. They are generally smaller and are formed

  horizontally
• dikes are plutonic rocks that intruded into cracks and crevices of

  existing rocks but they are slanted.
• EXAMPLES OF IGNEOUS rOCKS

  Basalt

  Peridotite

  Rhyolite
• SEDIMENTARY rOCKS Sedimentary rocks are formed from fragments ofother rocks. These

  smal pieces of rock settle on the riverbed in loose layers known as sediment. Over millions of years, the sediment accumulates, solidifies, and ultimately transforms into a compact, solid rock.
• There are three different types of sedimentary rocks: clastic, organic (biological), and chemical. 
• CLASTIC SEDIMENTARY ROCKS

  like sandstone, form from clasts, or pieces of other rocks
• ORGANIC (BIOLOGICAL) SEDIMENTÄRYROCKS

  like coal, form from hard, biological materials like plants, shells, and bones that are compressed into rock.
• CHEMICAL SEDIMENTARY ROCKS

  like limestone, halite, and flint, form from chemical precipitation.
• EXAMPLES OF SEDIMENTARY ROCKS

  CONGLOMERATE

  Made up of rounded pebbles which are cemented together.

  BRECCIA

  Made up of angular pebbles which are cemented together.

  SANDSTONE

  Sand cemented together forming a solid stone.

  SILTSTONE

  Silt cemented together to form a solid stone.

  SHALE

  Similar to siltstone but is composed of even finer grains of silt.
• Metamorphic rocks are formed when pre-existing sedimentary or igneous rock undergoes significant heat and pressure deep within the Earth's crust.
• The process of forming metamorphic rocks can lead to the transformation of the original rock into a completely new form.
• Metamorphic rocks form only 12% of Earth's land surface, but together with igneous rocks they compose 92% of Earth's crust.
• The range of temperature and pressure in which a protolith transforms into a metamorphic rock is 200 °C to 320 °c and 300 MPa to 600 MPa (MPa - Megapascals).
• METAMORPHIC ROCKS Metamorphosis is a combination of two

  Greek words: (Meta means after) and

  (Morphe means shape). Metamorphosis

  is the after shape. To metamorphose is to "change shape"
• Metamorphic rocks are divided into two categories- Foliates and Non-foliates
• FOLIATED/FOLIATION ROCKS

  When a rock with flat or elongated minerals is put under immense pressure, the minerals line up in layers.

  Example of this transformation can be seen with granite.
• NON-FOLIATED ROCKS are formed the same way, but they do not contain the minerals that tend to line up under pressure and thus do not have the layered appearance of foliated rocks.
• Common metamorphic rocks include slate , schist, gneiss, quartzite and marble.
• GNEISS

  (pronounced as

  nice, as in nice place)

  Form by high-grade metamorphosis. Its foliations display alternating dark and light

  colored bands, called gneiss banding.

  SLATE

  Fine-grained foliated metamorphic rocks derived from shale

  sedimentary rocks.

  
  

  MARBLE

  Non-foliated metamorphic rocks form from limestone.

  SCHIST

  Medium-grade metamorphic rocks with medium to large, flat, sheet-like grains.

  QUARTZITE

  H a r d non-foliated metamorphic rocks formed from quartz sandstone

  ( a sedimentary rocks)
• The Rock Cycle shows us how the different kinds of rocks on earth are related to each other. It also helps us understand how the earth's crust changes over long periods of time.