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

To help you rememberTo help you remember