Rocks and Rolls
RocksRocks
• Nearly all rocks are composed of one or more minerals
• Geologists classify rocks according to how they were formed
– Sedimentary – Igneous – Metamorphic
Sedimentary RocksSedimentary Rocks• Most abundant rock type on the Earth’s surface
– Sits on top of Igneous and Metamorphic rock• Example: Hardboiled Egg
– Sedimentary is the shell – Igneous and Metamorphic the egg
• Usually deposited in layers• Three types / textures:
– Based on where and how they were formed
ESRT – pg 7
FossilsFossils
Texture 1- ClasticTexture 1- ClasticInorganic – Land DerivedInorganic – Land Derived
• Most common type of sedimentary rock
• Formed on land…from non-living sediments
• Formed from sediment (clasts) that are compacted- then cemented together– Based on the size of the
grains they contain• See ESRT
Boulders
PebblesCobbles
ESRT – pg 6
ESRT – pg 7
Compaction and Cementation of Compaction and Cementation of Clastic Sedimentary RocksClastic Sedimentary Rocks
Sediments are
deposited
Sediments are
cemented together by
minerals
Sediments are compacted
‘squished together’
ConglomeratesConglomerates
• All size sediments (rounded)
• Fragments deposited by a glacier as it melted– Compacted and
Cemented together
BrecciaBreccia
• All size sediments (angular edges)
• Fragments deposited – Compacted and
Cemented together
SANDSTONE
SHALE
SILTSTONE
ESRT – Pg 2
• Minerals are dissolved in water• Water evaporates• Solid mineral left behind
(evaporite)Ex) salt water – when water
evaporates…salt left behind….’Halite’
Texture 2- CrystallineTexture 2- CrystallineChemically and /or organically formedChemically and /or organically formed
HALITE
DOLOSTONE
Texture 3 – Crystalline / BioclasticTexture 3 – Crystalline / Bioclastic
• Formed from plant and animal remains– Coal
• Often FOSSILSFOSSILS found in Bioclastic rocks!
COALCOAL
COALCOAL
FossilsFossils
Environment of FormationEnvironment of Formation
• Fossils, mud cracks and ripple marks – Help to identify where rock was formed
