2. What is a rock?What is a rock?
How does a rock form?How does a rock form?
What is/are the origin(s) of a rock?What is/are the origin(s) of a rock?
3. Definition of a RockDefinition of a Rock
Made of mineralsMade of minerals
Firm and coherentFirm and coherent
Aggregate of materialsAggregate of materials
4. Why Study Rocks?Why Study Rocks?
Rocks and minerals have economic value.Rocks and minerals have economic value.
Earth processes (volcanic eruptions,Earth processes (volcanic eruptions,
mountain building, weathering,mountain building, weathering,
earthquakes etc.) depend in some waysearthquakes etc.) depend in some ways
on the properties of rocks.on the properties of rocks.
Every rock contains clues about theEvery rock contains clues about the
environment in which it formed. Byenvironment in which it formed. By
looking at rocks closely we can figure outlooking at rocks closely we can figure out
events that happened earlier in Earthevents that happened earlier in Earth
history.history.
5. Components of a RockComponents of a Rock
ClastsClasts (fragments) or crystals large(fragments) or crystals large
enough to see the individual piecesenough to see the individual pieces
MatrixMatrix - fine-grained material- fine-grained material
between larger clasts or crystalsbetween larger clasts or crystals
CementCement - crystalline added after the- crystalline added after the
original rock formed (usually byoriginal rock formed (usually by
water flowing through the rock)water flowing through the rock)
9. The Rock CycleThe Rock Cycle
Rocks are divided into three groupsRocks are divided into three groups
based on their mode of origin:based on their mode of origin:
– igneous,igneous,
– metamorphic,metamorphic,
– sedimentary.sedimentary.
Each type of rock can be linked toEach type of rock can be linked to
another type by processes that actanother type by processes that act
on and within the Earth.on and within the Earth.
14. Rock Cycle (Basic)Rock Cycle (Basic)
Magma (molten rock)Magma (molten rock)
– crystallizes (cools and solidfies) at orcrystallizes (cools and solidfies) at or
near the surface to formnear the surface to form igneous rocksigneous rocks
15. Rock Cycle (Basic)Rock Cycle (Basic)
A rock, exposed at the surfaceA rock, exposed at the surface
undergoesundergoes
– weatheringweathering
disintegration of rock due todisintegration of rock due to
chemical/mechanical action,chemical/mechanical action,
– transportationtransportation oror erosionerosion
sediment moves downhill by gravity andsediment moves downhill by gravity and
taken somewhere else by wind or water,taken somewhere else by wind or water,
16. Rock Cycle (Basic)Rock Cycle (Basic)
A rock, exposed at the surfaceA rock, exposed at the surface
undergoesundergoes
– depositiondeposition
-comes to rest somewhere - in an ocean,-comes to rest somewhere - in an ocean,
river floodplain, swamp, sand dune etc., andriver floodplain, swamp, sand dune etc., and
– lithificationlithification
conversion into rock through compactionconversion into rock through compaction
and cementation and forms aand cementation and forms a
sedimentary rocksedimentary rock..
17. Rock Cycle (Basic)Rock Cycle (Basic)
A rock at or near the surface isA rock at or near the surface is
buried to great depth and isburied to great depth and is
subjected to:subjected to:
– intense heat (due to magma nearby?) orintense heat (due to magma nearby?) or
– pressure (due to mountain building)pressure (due to mountain building)
– The rock reacts to this change ofThe rock reacts to this change of
environment by becoming aenvironment by becoming a
metamorphic rockmetamorphic rock..
18. Alternate PathsAlternate Paths
The full rock cycle does not alwaysThe full rock cycle does not always
take place. Some "short cuts" are:take place. Some "short cuts" are:
– Sedimentary rock melts.Sedimentary rock melts.
– Igneous rock is metamorphosed.Igneous rock is metamorphosed.
– Sedimentary rock weathers.Sedimentary rock weathers.
– Metamorphic rock weathers.Metamorphic rock weathers.
20. Plate Tectonics and the RockPlate Tectonics and the Rock
CycleCycle
Cooling and crystallization ofCooling and crystallization of
magmamagma
– volcanic arcs, rifts/ridgesvolcanic arcs, rifts/ridges
MetamorphismMetamorphism
– At depth, especially within arcsAt depth, especially within arcs
UpliftUplift, weathering, erosion,, weathering, erosion,
depositiondeposition
– Especially where mountains built up atEspecially where mountains built up at
plate marginsplate margins
