Our Dynamic Earth

Our Dynamic Earth

Earth as a System• The Earth is an integrated system that consists of rock, air,

water, and living things that all interact with each other.

• Scientists divided this system into four parts:

• The Geosphere (rock)• The Atmosphere (air)• The Hydrosphere (water)• The Biosphere (living things)

Earth’s Interior• Scientists use seismic

waves to learn about Earth’s interior.

• Seismic waves are the same waves that travel through Earth’s interior during and earthquake.

• A seismic wave is altered by the nature of the material through which it travels.

Layers of the Earth

• Scientists divide the Earth into three layers:– The crust– The mantle– The core

• These layers are made up of progressively denser material toward the center of the Earth.

Processes and Forces that Affect the Lithosphere

• Rock Cycle• Weathering • Erosion• Soil Formation• Plate Tectonics• Earthquakes• Volcanoes• Humans

Rockin’ the Rock Cycle

Rock Cycle

• Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling

• Rocks can change to and from the three types through the rock cycle.

What is a Rock?

• Naturally-occurring mixtures of minerals, mineraloids, glass or organic matter.

• Rocks are divided into 3 groups based on how they were formed:

• IGNEOUS• SEDIMENTARY• METAMORPHIC

Igneous Rock

• Igneous rock is made when magma cools and crystallizes. (Igneous means “from fire or heat”)

Type of Igneous

Rock

Where does it Form?

How does it Cool?

What Size Grains does it have?

Example

Intrusive

Inside Earth

Slowly Large (Course)

Granite

Extrusive

Outside Earth

Quickly Small (Fine) or Glassy (Very Fine)

Basalt

Obsidian

Examples of Igneous Rock

Granite: Large/Course Grains

Basalt: Small/Fine Grains

Obsidian: Glassy/Very FineGrains

What happens to the Igneous Rock?

1. It can be weathered and eroded and turned into small pieces, called sediment, which can then be turned into a sedimentary rock.

2. It can be put under high heat or pressure and form a metamorphic rock.

3.Could melt and become magma again

Sedimentary Rock

1. Rock is weathered and forms sediments

– Sediments: smaller pieces of rock• Examples: Gravel, Sand, Mud, Soil

Sedimentary Rock

2. Erosion– The process by which weathered rock and

soil particles are moved from place to place by wind, water, gravity, glaciers, etc.

3. Deposition– The process by which weathered sediments

are laid down in a new location creating new landforms through “bedding”.

3. Deposition – Types of Bedding

1. Bedding – oldest sediments on the bottom, youngest sediments on top

2. Graded Bedding – biggest sediments on bottom, smallest on top (happens in water)

3. Cross Bedding – sediments are laid at an angle (ex: sand dunes)

Sedimentary Rock

4. Lithification - Sediments must be buried, compacted, cemented together to make a sedimentary rock.

• Examples of Sedimentary Rock:

Coal Sandstone Shale

What happens to Sedimentary Rock?

1. Could weather and erode to become sediments which cement and compact to form sedimentary rock

2. It can be put under high heat or pressure and form a metamorphic rock.

3.Could melt to form magma which cools and hardens to form igneous rocks.

Metamorphic RockLimestone (Sedimentary) Marble

Shale (Sedimentary) Slate

Granite (Igneous) Gneiss

• Formed from existing rocks.

• Are created by intense heat or intense pressure.

• Can be foliated = looks like it has layers (made from pressure)

• Can be non-foliated = does not look like it has layers (made from heat)

What happens to Metamorphic Rock?

1. Could weather and erode to become sediments that cement and compact to form sedimentary rocks

2. Could melt to form magma which cools and hardens to form igneous rocks

How are rocks redistributed?

• The core, mantle, & crust are one giant rock recycling machine changing the lithosphere.

Weathering

Weathering

Weathering is the breaking down of rocks and other materials on

the earth’s surface

Physical Weathering Breaks rock into smaller pieces without

changing the overall composition.

Examples- Biological Activity (tree roots and animals burrowing), Frost Wedging (water freezing inside cracks of rocks causing them to expand and break), Gravity

Chemical Weathering

Chemical reactions that change the overall composition of the rock.

Examples- Water (most important agent), Acid Rain on gravestones (dissolves minerals), Oxidation

Factors that determine the rate of weathering:o Composition

Granite more resistant than marble.o Physical conditions of rock

Cracks, holes, crevices – easier weathering Solid, unbroken – more weather resistant

o Topography: the position of the rocko Air pollutiono Exposure timeo Surface area exposedo Climate

o Cold Climates– mechanical weathering breaks down rocks rapidly

Warm, wet climates – chemical weathering breaks down rocks rapidly

Mechanical and chemical weathering work together

Erosion

5 Agents of Erosion

• Gravity• Glaciers• Wind• Water• Ocean Waves

Soil formation starts with…

• Weathering

• Erosion

• Deposition

Followed by…

• Some living organisms such as bacteria, fungi and insects.

• They die, decay and add nutrients to the soil.

So Basically…Soil is a layer at the surface of the earth composed of a mixture of weathered rock, organic matter, mineral fragments, water, and air which is capable of supporting the growth of plants impacting the lithosphere.

Plate Tectonics

What observations can you make about the shape of the

continents?

What’s interesting? Just 200 million years ago, this is what

the world looked like:

Plate Tectonics Tectonic plates - blocks of lithosphere

that consist of the crust and the rigid, outermost part of the mantle and glide across the underlying asthenosphere.

The continents are located on tectonic plates and move around with them.

The major tectonic plates include the Pacific, North America, South America, Africa, Eurasian, and Antarctic plates

Plate Boundaries

• Much of the geological activity at the surface of the Earth takes place at the boundaries between tectonic plates.

• Tectonic plates may separate, collide, or slip past one another.

Plate Boundaries

Divergent Boundary: Divergent Boundary:

Plate Boundaries

Divergent Boundary: Divergent Boundary: Plates are moving away

from each other Midocean ridges are

created and new ocean floor plates are created

Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates.

Rift Valleys

Plate BoundariesConvergent BoundaryConvergent Boundary: plates are moving

toward each other and are colliding (3 types)

Convergent Boundaries • Create

subduction zones, trenches

• Create near coast volcanoes

• Island arcs are created

• Mountain ranges are created – (example:

Himalayan Mountains)

Himalayan Mountains

Plate Boundaries

Transform Fault Boundary Plates are neither moving

toward nor away from each other, they are moving past one another.

Transform Fault Boundary The plates may move in

opposite directions or in the same directions but at different rates and frequent earthquakes are created (example: San Andreas Fault)

San Andreas Fault

o Noo Plates are destroyed as fast as

they are created (2 ways)o Plates may be subducted and

melted or may push be pushed upward to form mountains

So is the Earth getting bigger?So is the Earth getting bigger?

Tensional Force: stretching or pulling Creates a normal fault

What types of forces are created?

Compressional Force: force pushing something together Creates a reverse fault

What types of forces are created?

Shear or Transversal Force: a system of forces that

operates against a body from different sides

Creates a strike-slip fault

What types of forces are created?

Earthquakes• A fault is a break in the Earth’s crust along

which blocks of the crust slide relative to one another.

• When rocks that are under stress suddenly break along a fault, a series of ground vibrations, known as earthquakes, is set off.

• Earthquakes are occurring all the time. Many are so small that we cannot feel them, but some are enormous movements of the Earth’s crust that cause widespread damage.

Earthquakes The actual place

underground where the earthquake starts and rocks break producing vibrations is called the focus.

The place on the surface directly above the focus is called the epicenter

• Originate at the focus and travel outward in all directions

– Three Types: P wave, S wave, surface waves

• Foreshocks: small earthquakes that come before a major earthquake

• Aftershocks: Are adjustments in the crust after in earthquake.

– Smaller than main earthquake, but can cause as much or more damage. They can continue for weeks to months.

Seismic Waves

How do we Measure Earthquakes?

Earthquake waves are recorded by a seismograph and the recording of waves on paper is called seismogram

Locating the epicenter1. Lag time between the arrival of the P wave and the S

wave to the seismograph station is converted to a distance

2. A circle with a radius that equals the distance is drawn around the station.

3. Three stations can narrow down the location to where the circles intersect

Locating the focus: the lag-time of the surface wave will determine the depth of the focus

Measuring Earthquakes

Measuring Earthquakes

Where do Earthquakes Occur?

• The majority of earthquakes take place at or near tectonic plate boundaries because of the enormous stresses that are generated when tectonic plates separate, collide or slip past each other.

• Over the past 15 million to 20 million years, large numbers of earthquakes have occurred along the San Andreas fault in California, where parts of the North America plate and the Pacific plate are slipping past one another.

Where do Earthquakes Occur?

Landslides Avalanches

Earthquake Dangers

Volcanoes

A volcano is a mountain built from magma, or melted rock, that rises from the Earth’s interior to the surface, and can occur on land or in the sea.

Volcanoes are often located near tectonic plate boundaries where plates are either colliding or separating from one another.

The majority of the world’s active volcanoes on land are located along tectonic plate boundaries that surround the Pacific Ocean.

Volcanoes: The Ring of Fire

The Birth of a volcano

What comes out of volcanoesWhat comes out of volcanoes??

•Lava•Tephra•Gases

Tephra• Basically, rock fragments• Also known as pyroclastic rock

fragments.• There are many different possible

sizes, from very small (volcanic ash or dust to much larger rocks (called volcanic bombs)

GASES

water vapor, carbon dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, chlorine

Two factors determine the type of eruption:

Amount of water vapor & other gases in the magma

The chemical composition of the magma

Types of Volcanic Eruptions

Trapped gases under high pressure will violently explode

Has granitic magma

The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions

Explosive Eruptions

The eruption of Mt. St. Helens in 1980

• Low Pressure gas• Has basaltic

magma (is more fluid and will flow instead of explode)

…and has low water content

Examples: Hawaii

Quiet Eruptions

A typical Hawaiian Eruption

Types of volcanoes

Local Effect of Volcanic Eruptions

Clouds of host ash, dust, and gases can flow down the slope of a volcano at speeds of up to 200 km/hr and sear everything in their path.

During and eruption, volcanic ash can mix with water and produce mudflow (lahar) that runs downhill.

In addition, ash that falls to the ground can cause buildings to collapse under its weight, bury crops, damage the engines of vehicles, and cause breathing difficulties.

Global Effect of Volcanic Eruptions

• Major volcanic eruptions can change Earth’s climate for several years.

• In large eruptions, clouds of volcanic ash and sulfur rich gases may reach the upper atmosphere, and spread across the planet reducing the amount of sunlight that reaches the Earth’s surface.

• The reduction in sunlight can cause a drop in the average global surface temperature.

Human Impact on the Lithosphere

Urbanization• Destroying natural areas

can reduce the beauty of an area and have a potential economic impact.

• Rapid development can result in very high levels of erosion and sedimentation in river channels.

• Pollution of soils is possible by leaking gas tanks and other chemicals.

Agriculture• Agriculture takes space.• Use of chemical

pesticides, insecticides and fertilizers can contaminate soil and affect soil fertility.– Organic fertilizers are

better.• Planting the same crop

over and over can strip vital minerals out of the soil.– Crop rotation can help.

Deforestation• Cutting down all the trees in an area

loosens the soil and makes it very easy for extreme erosion to occur.

• One solution is replanting and a system of harvesting that thins out the area.

Overgrazing• Overgrazing is the removal of

excessive amounts of plant growth by animals in one area. This accelerates erosion and strips away topsoil, resulting in no plants able to grow.

• It is best to rotate animals among pastures.

Mining

Strip Mining• Underground mining requires digging out large areas, increasing the risk for sinkholes and cave ins.

• Strip mining destroys the environment.• Mine operators must reclaim the land after

mining is finished (put the land back together and restore it to its original condition).

Harvesting Peat• Peat is an accumulation of partially decayed

vegetation. Eventually, peat can turn into coal and be burned for fuel.

• Advantages– low sulphur content – minimal mercury content– low ash content energy – values equivalent to coal, less expensive than oil

and natural gas and competitive with other biofuels– minor engineering retrofit needed when

substituted for, or blended with, coal• Since peat forms nearer to the surface, it

requires less digging.

Drilling for Oil and Natural Gas• Oil and Natural Gas

are nonrenewable resources.

• Drilling can cause the lithosphere to be disturbed and can cause earthquakes.

• Soil and groundwater can also be contaminated.– Fracking is a hot

political topic.

Human Activity and the Coast

• As more and more people retire, there is more development on our coast.

• Removal of vegetation at the coast can cause serious erosion.

• Man made erosion control, like sandbags, can make erosion worse downshore.

• Erosion causes houses to be condemned and potentially fall into the ocean.