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Rocks Part #2

Rocks Part #2. Sedimentary rocks. Formed by sediments being buried and compressed. Form in layers (Law of Superposition) oldest layers on the bottom, newest on top If no overturning has Occurred Sediments get sorted so most are formed by material of the same size. Clastic

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Rocks Part #2

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  1. Rocks Part #2

  2. Sedimentary rocks • Formed by sediments being buried and compressed. • Form in layers (Law of Superposition) • oldest layers on the bottom, newest on top • If no overturning has Occurred • Sediments get sorted so most are formed by material of the same size.

  3. Clastic Formed from fragments of other rocks Cementation occurs Sediments are usually sorted by water Gravels form conglomerates Sands form sandstones Silts form clays Chemical Form when mineral grains fall out of solution or evaporate Example - rock salt (halite) Organic Form from the remains of plants and animals Ex) – coal (plants) some limestones (shell fragments) Three Types of Sed. Rocks

  4. Fossils Types of Fossils #1 Original remains When the organism is preserved in something like ice or sap (examples insects in sap or woolly mammoths in ice) #2 Replaced remains The soft parts decay and are filled back in by minerals (example – petrified wood) #3 Mold and cast The soft parts buried and an impression is made in the material. The soft parts then waste away and you are left with an empty cavity that looks like the organism. #4 Trace fossils Impressions left behind that form in rock such as footprints burrows etc. Special Structures

  5. Special Effect cont. • ripple marks • water ripples left in mud then dry • mud cracks • mud dries and cracks the forms into a rock

  6. Metamorphic Rocks • When a rock gets heat and or pressure added to it and turns into a new type of rock. • Doesn’t completely melt but comes close • Minerals line up and get into layers

  7. Types of Metamorphism • #1 Dynamic metamorphism (regional metamorphism) • When Earth’s large plates move the friction or collisions build up enormous heat and pressure and change the rock • Most metamorphic rocks are formed this way • #2 Thermal metamorphism (contact metamorphism) • When magma gets into rock layers it changes the rocks it comes in contact with.

  8. Examples of metamorphism • granite (Igneous) becomes gniess • shale (Sed) becomes slate • limestone (Sed) becomes marble

  9. Rock cycle • Shows how the same material can go through several changes and become all three types of rocks over and over again.

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