CHAPTER 3THE DYNAMIC EARTH

Four “spheres” of Earth:

Earth is an integrated system in which all of these parts interact with each other:

Earth = Geosphere + Atmosphere + Hydrosphere +

Biosphere

The earth is constantly changing.

Geosphere

Definition: the solid part of the Earth that consists of all rock and the soils and sediments on Earth’s surface

Basic layers:crust, mantle, core

GeosphereMore detailed layers of the earth:1. Crust - thin outer layer of the earth 2. Lithosphere – crust plus rigid upper mantle divided into huge pieces called tectonic plates3. Asthenosphere – solid, plastic layer of the mantle between the lithosphere and the mesosphere; made up of rock that flows very slowly; this layer is what moves the tectonic plates4. Mesosphere – lower layer of the mantle between the asthenosphere and the core

(see pg. 61)

5. Outer core – outer shell of earth’s core made of liquid nickel and iron

6. Inner core – sphere of solid nickel and iron at the center of the earth

Complete this summary chart for layers of the earth

Layer Physical state

Temperature (°C)

Common elements

Crust

Mantle

Outer core

Inner core

The earth’s major tectonic plates – label them on your handout

Learn the 10 listed in Figure 4 on page 62 of your textbook

Continental driftTectonic plates – huge pieces of the earth that

slowly glide across the underlying asthenosphere, continents are located on tectonic plates and move around with them, called theory of continental drift (proposed by Alfred Wegener in 1912, not accepted until 1950s)

Model for tectonic plates:A Milky Way bar Chocolate on top = crust + lithosphere of earth

Notice how it breaks into chunks (tectonic plates) that you could push around on top of the caramel Caramel layer = asthenosphere (semi-solid, or “plastic”) Nougat layer = rest of mantle under asthenosphere (rigid)

Why tectonic plates move

http://www.bing.com/videos/search?q=animation+tectonic+plates&view=detail&mid=F3C8F4F217FABEC2F9F8F3C8F4F217FABEC2F9F8&first=21&adlt=strict#view=detail&mid=3370D53D3F37B58BB3EB3370D53D3F37B58BB3EB

Tectonic plate movementThree ways tectonic plates can move:1. Divergent plate boundaries – where

tectonic plates are moving away from each other; new crust forms from magma that rises to earth’s surface between the two plates

2. Convergent plate boundaries – two plates move toward each other; subduction may occur, where one plate goes under the other and the crust is destroyed (melts) as it descends toward the hotter core of the earth

3. Transform faults – crust is not formed nor destroyed; plates move horizontally and slip past each other; may be sudden causing an earthquake

Review:Name three types of plate boundaries and explain how they are moving.

Pangaea

The earth’s land masses were once a supercontinent called Pangea – around 225 million years ago

Pangaea animation

https://www.youtube.com/watch?v=WaUk94AdXPA&safe=active

Plate boundaries

At plate boundaries, there is a lot of activity – three things can happen:

1. Mountain formation (Ex: Himalayas) – between the Eurasian and Indian plates, presence of mountains influences life forms present (due to factors such as elevation, rain shadow, etc.)

2. Earthquakes can occur at tectonic plate boundaries and along fault lines (definition of fault: a break in the earth’s crust)

California’s San Andreas Fault

Earthquakes Earthquakes are measured on the Richter

scale. The smallest earthquake that can be felt is a

magnitude 2.0. The largest ever recorded was a 9.5 magnitude earthquake.

Earthquakes can occur almost anywhere. Learn the information in this diagram:

What are some environmental effects of earthquakes?

slope movements ground cracks ground settlements surface waves/tsunamis

New Madrid Fault A fault zone near the southeastern U.S. – series of earthquakes led to the formation of Reelfoot Lake near Memphis in 1811-1812

3. Volcanoes Volcanoes are built from magma –melted rock. Volcanoes are often located near tectonic

plate boundaries. Volcanoes can occur under the sea as well as

on land, can form islands such as the Hawaiian Islands

“Ring of fire” – many volcanoes are found around the Pacific plate boundary

Local effects of volcanoes:

• lava flow may engulf and bury the land, but new soil and vegetation eventually develop

• volcanic ash slowly weathers to form rich, loamy soils.

Global effects of volcanoes:

• clouds of volcanic ash and sulfur-rich gases can reach the upper atmosphere and reduce amount of sunlight that reaches earth (ex. Tambora 1815, “the year without a summer”)

On May 18th, an earthquake measuring 5.1 on the Richter scale caused a landslide on the northern flank of the volcano, which in turn exposed the crypto dome below, resulting in a sudden release of pressure and a cataclysmic eruption in the form of a lateral (sideways) blast. The blast zone consisted of 230 square miles with the eruption leaving a 'lunar' landscape in its wake.

The effects of the eruption included:*Released equivalent of 500 atomic bombs* 57 people died in the eruption - most from poisonous gases;* large number of wildlife were killed by the blast and the volcanic ash with nothing surviving in the blast zone* flooding resulting from blocked rivers washed away road and rail bridges* crops were ruined and livelihoods of loggers were devastated with large areas of trees being flattened like matchsticks.

Mt. St. Helen’s, Washington, 1980

Review: Name three things that can happen at plate boundaries.

Another force that shapes our environment: erosion

Definition: removal and transport of the Earth’s surface material by a natural agent, such as wind, water, ice or gravity

Large scale: Grand Canyon and Yosemite valley

Soil: the foundation for life

Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers

Soil is important because:1. It provides most of the

nutrients needed for plant growth, and subsequently consumer growth.

2. It is the primary filter that cleanses water as it passes through.

3. It is a major component of the earth’s water recycling and water storage processes.

Components of soil

25% air (mostly N and O)25% water45% mineral5% organic matter

Amounts of air and water vary

Where does soil come from?

Formation of soil depends on 5 factors:1. climate 3. biologic activity 5. time 2. terrain 4. geology

It takes 15 to 100s of years to form one cm of soil!

*Parent material = the base geologic material of soil

**Bedrock = the continuous mass of solid rock comprising the Earth’s crust

*

**

Weathering contributes to the formation of soil

Weathering = the physical, chemical, or biological processes that break down rocks to form soil

Physical (mechanical) • wind and rain • no chemical changes in

the parent materialChemical

• substances chemically interact with parent materialBiological

• organisms break down parent material

Decomposition contributes to the formation of soil

Decomposition is the breakdown of organic material (dead organisms, waste products, leaves, etc. that contain carbon) into tiny pieces that become part of the soil

What organisms carry out decomposition?macroscopic: worms, insects,

centipedesmicroscopic: bacteria, fungi, protists

Decomposition by organisms is a way for them to get energy

Decomposition Process

Organic material – dead leaves, dead organisms, waste

Organic material is broken down in the presence of oxygen by worms, insects, bacteria and fungi

Nutrients accumulate in the soil and are used by other organisms

As organisms decompose organic material, they release carbon dioxide into the air

Soil Horizons: Layers of mature soil

O horizon – organic material, leaf litter, many organisms live here

A horizon – topsoil layer, zone of accumulation of organic matter and nutrients

These top 2 horizons contain:- the roots of most plants- billions of living things (bacteria, fungi, earthworms, insects, etc.)

Soil Horizons: Layers of mature soil

B horizon – subsoil, accumulates iron, clay, aluminum and organic compounds that leach down from above

(leaching: process in which water seeps down through open spaces or pores in soil, dissolving minerals and organic matter and carrying them to lower layers)

Soil Horizons: Layers of mature soil

C horizon – parent material, contains large lumps or shelves of rock

R horizon (under C horizon)- bedrock

Soil Particles

Three types, based on size:1. Sand: 2.0-0.05 mm2. Silt: 0.05-0.002mm3. Clay: less than 0.002mm

Relative amounts determine soil texture

Soil Textural Classification

Soil PermeabilityDefinition: the rate at which water and air move from

upper to lower soil layersThe more spaces there are between soil particles, the

more permeable it isPlants need good drainage, but not too much

Plants are like Goldilocks

Sandy soil: This soil is too permeable – water runs right through

Clay soil: This soil is too impermeable – water can’t get through

Loam: This soil is just right! (mixture of sand and clay)

Which is which?Sand on leftLoam in middleClay on right

Other soil characteristics that are important to plants

Nutrient content – three important nutrients found in soil:

1. nitrogen (N)2. phosphorus (P)3. potassium (K)

pH – if soil is too acidic or basic, plants can’t grow

Think and review: What does weathering contribute to soil? What does decomposition contribute to

soil? What is a soil profile and what are the

major layers?

SedimentDefinition:Sediment is solid material that is moved

and deposited in a new location. Sediment can consist of rocks and minerals, as well as the remains of plants and animals. It can be as small as a grain of sand or as large as a boulder. 

SedimentIn Env. Science, we usually refer to sediment as particles that are

moved by flowing water; sediment settles out when the flow of water slows;

Some sediment in water is a normal and important part of ecosystems; significant because it adds nutrients to soil after flooding recedes

Too much sediment in aquatic ecosystems can have a negative impact on organisms; loss of vegetation on land leads to more erosion and more sediment in flowing water

Sedimentation from development in Birmingham makes its way into Bayview Lake of Village Creek of the Black Warrior (Jefferson Co.)Photo by Nelson Brooke. Flight provided by Southwings.org

Sediment

Over millions of years, layers of sediment can form sedimentary rockExposed rock undergoes weathering and erosion, water carries sediment through rivers to the ocean where it settles to the bottom in layers

Think and review:How does the geosphere affect the biosphere?How does the biosphere affect the geosphere?