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The world of rocks; GeologyAn art of spying

Deepak C. Srivastava IIT Roorkee, Roorkee, Uttarakhand

What is Geology?Science of the Earth...just like chemistry and physics!What is different about Geology?Special challenge- controlled experiments?The rates of geologic processes are almost always slower than the rates of human effects on the environment.Geologists use millions of years as the standard unit of time:Some geologic features take millions of years to form.

Carr CliftonOthers take seconds

John Sanford/Photo Researchers5

Spying the signatures of nature

Objective?Ex. Rock type?

Types of signatures depend on origin of rocks3. Metamorphic2. Sedimentary1. IgneousThree types of origin:Magma- the molten rock material3 components:Liquid = meltSolids, if anyVolatiles = dissolved gasesIgneous originSolidification of magma Igneous rocks

Igneous rocks(Magma) Plutonic

(Lava) Volcanic

Surface

Deep or Shallow/surface?Glassy Texture

Lava or Magma?TextureGrain size?

Domestic Example?

Lava or Magma?

Interlocking textureLava or Magma?Igneous rocks?

Examples:Tin, Tungsten, Diamond, Platinum, mica. Weathering (Breaking)TransportationDeposition

Sedimentary rocks?Let us spy the evidence for these processes in rocks

Three componentsClastMatrixCement

Clast, Matrix, CementEaES 350-619

Sedimentary laryeringWhat happens when you go to?

Kashmir in wintersRajasthan in summers

Metamorphic rocksResults of Stress Compressive Stress

Shear StressCauses Foliation

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Evidence of Metamorphism Differential pressure squashes rock and included features2. Flattened PebblesConglomerateMetaconglomerate22

Evidence of Metamorphism

23Any pre-existing rocks can be metamorphosed

Rock Cycle25