Geology

Chapter 15

Geology

The science devoted to the study of dynamic processes occurring on the Earth’s surface and

in its interior

Essential Question #1

What are the characteristics of the

three major concentric zones of earth?

Three Concentric Zones• Core – innermost zone– Extremely hot– Solid inner part surrounded by liquid molten material

• Mantle – middle zone– Outermost part is solid rock– Asthenosphere = inner part made of hot partly melted

pliable rock that flows

• Crust – outermost zone– Continental crust– Oceanic crust

Earth’s Crust and Upper Mantle

Lithosphere = Crust and outermost Mantle

Fig. 15-3, p. 337

Spreading center

Ocean trench

Plate movement

Subduction zone

Oceanic crust

Continental crust Continental

crustMaterial

cools as it reaches the outer mantle

Cold dense

material falls back through mantle

Hot material

rising through

the mantle

Mantle convection

cell

Two plates move towards each other. One is subducted back into the mantle on a falling convection current.

Mantle

Hot outer core

Inner core

Plate movement

Collision between two continents

Tect

onic

pl

ate

Oceanic tectonic

plate

Oceanic tectonic plate

Oceanic crust

Essential Question #2

How does the movement of tectonic plates shape the earth’s

surface and other zones?

Tectonic PlatesConvection cells (currents) in the mantle move

large volumes of heat and rocks in loops, causing the movement of large rigid plates (lithosphere)

on the earth’s surface.

Tectonic Plate Boundaries

• Convergent – push two plates together

• Divergent – spread plates apart (oceanic)

• Transform – plates slide past each other

Tectonic Plate Boundaries• Convergent Plate Boundaries– Subduction - Continental plate usually pushes oceanic

plate down into mantle– Forms a trench in ocean & mountains on land

• Divergent Plate Boundaries– As oceanic plates spread apart, molten rock (magma)

pushes up the cracks forming ocean ridges

• Transform Faults– Plates slide and grind past one another along a

fracture (fault) in the lithosphere– Mostly in oceans– San Andreas Fault , CA

Major Tectonic Plates & Boundaries

Volcanos

Often form along the boundaries of tectonic plates where magma can escape in the form of lava

Ring of FireHuge ring of volcanic and seismic activity

Includes 452 volcanos; over 75% of world’s active and dormant volcanos

About 90% of the world’s earthquakes & 81% of the world’s largest earthquakes occur here

Earthquakes• Colliding plates create tremendous pressures in the crust

• Earthquakes occur when stresses cause rocks to suddenly shift and break, forming faults

• Abrupt movement of faults release stored energy in the form of seismic waves, which move in all directions through the surrounding rock

– Focus = place where an earthquake begins

– Epicenter = place on the surface directly above the focus

Earthquake in Haiti – January 2010

• 7.0 Magnitude, followed by at least 52 aftershocks 4.5 or greater

• Over 220,000 dead; damaged 250,000 residences & 30,000 commercial buildings

• Despite humanitarian aid efforts, over 370,000 people still without homes today

Ocean Earthquakes & Tsunami’s

Indian Ocean Tsunami - 2004• 9.15 Magnitude earthquake on ocean floor generated

waves as high as 100ft

• Killed ~228,000 people in Indonesia, Thailand, Sri Lanka, South India & Eastern Africa

Japan Tsunami - 2011• 9.03 magnitude earthquake on ocean floor generated

waves as high as 133ft

• Over ~16,000 reported dead/missing

• Estimated economic cost $235 billion (US) – costliest natural disaster in world history

• https://www.youtube.com/watch?v=av1Ieq0q06Q

Essential Question #3

How do physical, chemical and biological weathering

generate soil?

Weathering

The physical, chemical, and biological processes that break down rocks and minerals

into smaller particles that help build soil.

Weathering Physical (Mechanical) Weathering• Large rock broken down into smaller pieces

Chemical Weathering• One or more chemical reactions slowly

dissolve the minerals in rocks

Biological Weathering• Conversion of rocks or minerals into smaller

particles through the actions of living things

Fig. 15-6, p. 340

Parent material (rock)

Biological weathering

(tree roots and lichens)

Chemical weathering

(water, acids, and gases)

Physical weathering

(wind, rain, thermal expansion and contraction, water freezing)

Particles of parent material

Erosion

The process by which material is dissolved, loosened, or worn away from one part of the

earth’s surface and deposited elsewhere

Mass Wasting

When rock and soil become detached from underlying material and move downhill under

the influence of gravity

Essential Question #4

What are the three classes of rocks, and how are

they recycled by the rock cycle?

Rock• A solid combination of one or more minerals

that is part of the earth’s crust

3 Types of Rock• Igneous– Forms when molten rock (magma) wells up from the

earth’s upper mantle, cools, and hardens

• Sedimentary– Forms from sediment produced when existing rocks are

weathered and eroded into small pieces– Compaction (pressure) + Cementation (minerals seeping

through sediment deposits) bind particles forming rock

• Metamorphic– Forms when a preexisting rock is subjected to high

temperatures / pressures, chemically active fluids, or a combination

Fig. 15-8, p. 343

Erosion

Transportation

Weathering

Deposition

Igneous Rock

Granite, pumice, basalt,

lava rock

Sedimentary Rock

Sandstone, limestone, shale,

dolomite, bituminous coal

Heat, pressure

Cooling

Heat, pressure, stress

Magma (molten rock)

Melting

Metamorphic RockSlate, marble, gneiss,

quartzite

Soil: A Renewable Resource

Chapter 3

Essential Question #5

What is soil and why is it important?

Soil

A thin covering over most land that is a complex mixture of eroded rock, mineral nutrients,

decaying organic matter, and billions of living organisms (most of them microscopic

decomposers)

Soil is a renewable resource that is renewed very slowly

(100’s to 1000’s of years)

Ecological Services of Soil• Supply nutrients to producers

• Cleanses & stores water

• Important in biogeochemical cycling– Decomposes organic matter

• Helps control climate by sequestering carbon

• Habitat for soil organisms

• Scientific research - antibiotics

Economic Services of Soil

• Supports agriculture industry– Food, feed, fiber, fuel, etc

• Provides food security

• Stores solid waste

• Foundation for cities and towns

Soil & Human Civilization

• Human activities have accelerated natural soil erosion since the beginning of agriculture

– Mismanagement turns soil into a nonrenewable resource

• Sophisticated civilizations such as the Mayans, Easter Island, Harappan (India) ended as a direct result of mismanaging soil

Essential Question #6

What are the three sizes of particles that compose soils, and how do they

determine soil texture?

Soil Particle Size

• Sand– Largest

• Silt– Medium

• Clay– Smallest

Physical Properties of Soils• Soil Texture

– Relative proportions of sand, silt & clay particles in a soil

– Measured using Soil Triangle– LOAM Soil = BEST for plant growth

• Permeability– The rate at which water moves through

soil– Porosity – the amount, size and

arrangement of pores between particles

• Water Holding Capacity– Ability of pores to hold water for plant use

Soil Texture Triangle

Chemical Properties of Soil• Nutrients– Primary: Nitrogen (N), Phosphorus (P), Potassium (K)– Secondary: Sulfur (S), Calcium (Ca), Magnesium (Mg)

• pH– Affects availability of plant nutrients– Optimal pH between 5.5 – 7.5– More acidic soils hold more toxic nutrients– Affects soil organisms & nutrient cycling

• Salinity– Salts come from irrigation water, fertilizers, composts &

manure

Soil Salinity and Interpretation

Organic Matter & Soil

Microorganisms are the driving force for nutrient release to plants