GEOLOGY

What is geology?

It is essentially the study of the

earth and it’s dynamic processes.

Features and processes of rocks,

the earth’s interior and surface.

Structure of the Earth

• Made up of three main parts:

1. Core

2. Mantle

3. Crust

1. Core – Inner core is solid mainly made out of iron and nickel. Outer core is liquid. Extremely hot (4,300*C)

Structure of the Earth

2. Mantle – Largest zone of the interior. Solid rock made of mainly iron, silicon, oxygen and magnesium.

Near the outermost part, is a very hot, partially melted zone of rock that flows like soft plastic. This part is called the athenosphere.

The outermost part is called the lithosphere.

Structure of the Earth

3. Crust – the outermost and thinnest layer of the earth. Consists of the continental crust and oceanic crust. Made up of eight elements, mostly oxygen, silicon, aluminum, iron, etc.

The lithosphere contains the outermost part of the mantle and all of the crust.

Internal Processes of the earth.

Convection cells

and mantle plumes

PLATE TECTONICS

• The outer most crust (or lithosphere) are made up of solid rock plates that move on the athenosphere.

• The theory explaining the movements of plates and the processes that occur at their boundaries is called plate tectonics.

• Pgs. 214-215 in text

Plate Boundaries

• Divergent plate boundary – when the plates move apart in opposite directions.

• Forms volcanoes and earthquakes.

Plate Boundaries

• Convergent plate boundary – when the plates move together.

• The denser plate is subducted under the lighter plate. This forms a trench.

• Can cause earthquakes and volcanoes.

Plate Boundaries

• Places where plates

slide past each other are called transform boundaries (fault).

• Causes earthquakes.

External Processes of the Earth

• External processes are driven by the energy of the sun. (instead of the heat of the earth in internal processes)

• External processes tend to degrade the crust. (instead of the changing/renewal processes of internal processes)

External Processes of the Earth

• Erosion

– is when the earth’s surface is worn away by wind, water, or human influence.

– Weathering is the main natural means for erosion.

What can cause soil erosion?

• 1. Wind

• 2. Water

• How do humans affect soil erosion?

Shopping malls

Urban sprawl – destroying natural habitats

Farming/Timber

Irrigation

Erosion

The Rock Cycle

• The slowest of the earth’s natural processes. (timescale of millions of years)

• Responsible for all of our deposits of fossil fuels and minerals.

• Driven by both internal and external processes.

• Rocks move between three major types.

IGNEOUS ROCK

• Formed above or below the earth’s surface when magma cools and hardens.

• Examples: Pumice,Granite, Quartz, Feldspar.

• Make up most of the earth’s crust.

METAMORPHIC ROCK

• Formed mainly by internal processes

• When igneous and sedimentary rock is exposed to high temperatures, pressure, or chemicals.

• Examples: Slate and marble

SEDIMENTARY ROCK

• Formed from erosion of rock.(external processes)

• Sediment is collected, buried, and compacted to bond the pieces of rock together. (usually under water)

• Examples: shale, sandstone, bauxite, and coal.

ROCK CYCLE

Volcanoes

• What is a volcano?

• A cone which is formed above and around

a vent by accumulations of erupted

volcanic materials like ash, pumice, lava

flows and other volcanic rocks. "Volcano"

can refer to both the vent and the cone.

Volcanoes• How are they formed?

– Mainly due the pressures caused at the boundaries of the plates.• However there are “hot spots” that are far from the boundaries. • Hot spots are fixed places within the mantle or oceanic

lithosphere, where rocks melt to generate magma.• Where a hot spot lies beneath a continental plate the hot spot

may generate enormous volumes of lava that accumulate layer upon layer.

• The Yellowstone hot spot has been

active for at least 15 million years.

• The Hawaiian hot spot, for example, has

been active at least 70 million years,

producing a volcanic chain that extends

3,750 miles (6000 km) across the northwest Pacific Ocean.

Earthquakes

• What are earthquakes?

– The sudden fracture or shifting of fractures due to stress in the lithosphere.

• Where do they occur?

– 90% of earthquakes occur at the plate boundaries.

Characteristics of an Earthquake

• After the sudden shift, the energy is released as a shock wave.

• The focus is the initial point of the shock wave.

• The epicenter is the surface location over the focus.

Severity of Earthquakes

• The magnitude is the measure of the amount of energy released.

• Shock wave is measured by a seismograph.

• Richter scale (<4 insignificant, 4-4.9 minor, 5-5.9 damaging, 6-6.9 destructive, 7-7.9 major, and over 8 great.

Severity of Earthquakes

• Primary effects –shaking, displacement of ground.

• Secondary effects –rockslides, subsidence, flooding, fires, or tsunamis.

Severity of Earthquakes