Dynamic Earth

Welcome to GEO 101

Introduction to Geology

… so what is Geology?

… not just rocks!

Geology is ...study of Earth and planetary bodies

processes responsible for formationprocesses that modify

all areas of geology have either economic or environmental importance:

earth resourcestopography (study of landforms and processes responsible for their formation) natural hazards (floods, volcanism, earthquakes) waste disposal and pollution cleanupclimate change

mineralogy - petrology - geochemistry - volcanologystratigraphy - sedimentology - paleontologygeomorphology - surficial geology - hydrogeologystructural geology - tectonics - geochronologysolid-earth geophysics - rock mechanics

Geology is a physical science with many sub-areas of study or sub-disciplines:

environmental and groundwater use (environmental geology)oil and gas exploration and exploitation (petroleum geology)metal and non-metal mineral exploration and exploitation (economic geology)

Geology is also an applied science that interfaces with engineering and deals with:

... so what is the modern context in which we will

be examining Earth?

a system of various subsystems or related parts (atmosphere, hydrosphere, biosphere, and solid earth) interacting in organized fashion

The Dynamic Earth

LayersCrustMantle

upperlower

Outer coreInner core

du

ctileb

rittle

asthenosphere

lithosphere

initially homogeneous, but with cooling separated into distinct concentric layers:

Layer Thickness NatureInner core 1216 km solid iron-nickel alloyOuter core 2270 km liquid iron-nickel alloyMantle ~2885 km solid (Mg-rich silicates)

upper (shallow) - intermediate densitylower (deep) - high density

Crust ≤65 km solid (low to intermediate density silicates)

Oceanic Crust (5-10 km) - high density (Fe-Mg rich)Continental Crust (30-65 km) - low density (Fe-Mg poor)

igneous - formed by cooling and solidification of molten rock (magma)sedimentary - formed by precipitation from solution, compaction of plant and animal remains, or cementation of particles from pre-existing rocksmetamorphic - formed below surface under high temperatures and pressures from pre-existing rocks

solid Earth composed of rocks divided into three groups based on mode of formation:

different rock types related to each other by: rock cycle

Geologists interrelate Earth processes, rock

types and physical features through global

pattern of change described by what has

become known asPlate Tectonic Theory

Earth's brittle outer shell or lithosphere (crust and uppermost mantle) broken into

coherent pieces or plates that move slowly over the ductile asthenosphere

three major plate boundary types marked by earthquakes, volcanism, or both

plates move

apart from each

other with gap filled by molten

rock creating

new crust

divergent plate boundary

separation marked by long mountain ranges on ocean floors and deep linear

valleys (rift zones) on continents

Mid-AtlanticRidge

East PacificRise

IndianRidge

IndianRidge

Rio GrandeRift

East AfricaRift

convergent plate boundary plates move toward

one another and where crusts of adjacent plates have different

densities, denser plate is forced

down or subducted beneath other

plate convergence with oceanic crust subducted beneath lower density continental crust

plate convergence

with oceanic crust subducted beneath oceanic crust

plate convergence of continental crust against continental crust

marked by mountain belt or subduction zone with deep oceanic trench, volcanism

and inclined earthquake (Benioff) zone

plates slide past one another

transform plate boundary

crust neither created nor destroyed(earthquakes but no or extremely limited

volcanism)

Plate boundary CharacteristicsBoundary Topography Igneous Metamorphic Sedimentary Earthquakes

divergent-types

ocean MOR basalt hydrothermal deep ocean shallow

continent cont. rift basalt & rhyolite

low-T/low P coarse clastics

shallow

convergent-types

continent-continent

mountains granites high-T/low P regional

clastics shallow intermediate

deep

continent-ocean

volcanic arc & trench

andesite high-P/low T regional

clastics shallow intermediate

deep

ocean-ocean

volcanic arc & trench

andesite high-P/low T regional

clastics shallow intermediate

deep

transform-types

ocean very little none/limited basalt

none none shallow

continent very little none/limited basalt

none none shallow intermediate