Inside the Earth
National Park Project

Earth's Changing Surface

Weathering & Erosion


Weathering The process that breaks down rock and other substances on the Earth's surface. Heat, cold, water, ice, oxygen, and carbon dioxide all contribute to weathering.
Mechanical weathering - when rock is physically broken down into smaller rocks. Causes include: freezing & thawing, release of pressure, plant growth, action of animals, and abrasion.
Chemical weathering - the breakdown of rock through chemical changes. Causes include: the action of water, oxygen, carbon dioxide, living organisms & acid rain.
Rate of weathering - Two most important factors include type of rock & climate
Erosion The removal of rack particles by wind, water, ice, or gravity.

Weathering & Erosion Video (21 min)

Surface Features using maps

Topography - the shape of the land including the area's elevation, relief, and landforms
Elevation - the height above sea level on the Earth's surface
Relief - the difference in elevation between the highest and lowest parts of an area
Landforms - a feature of topography, such as a hill or valley, formed by the processes that shape the Earth's surface.

Three main types of landforms

Plains - nearly flat of gently rolling land with low relief. Elevation varies.
Mountains - landforms with high elevation and high relief
Plateaus - landforms with high elevation and a more or less level surface, low relief

How are landforms represented on flat maps?
How to read Contour Maps
Matching Contour maps
Mapping Topics
How to read Topographic Maps
Contour Line Basics
Map Skills


Mineral site for kids
United Streaming - What exactly are minerals?
Mineral Outline.DOC

1. Naturally Occuring
2. Inorganinc
3. Solid
4. Repeating crystal pattern
5. Definite chemical composition

How to identify
1. Streak
2. Luster
3. Color
4. Hardness
5. Density
6. Crystal Pattern
7. Special characteristics

How minerals are formed
1. Magma & Lava
2. Solutions that evaporate above ground
3. Hot water solutions below ground


Rock Outline.doc

Pictures of each rock type
Types of Rocks

Rock Cycle

Rock Cycle
Rock Cycle Interactive
Rock Cycle Interactive

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How Plates Create Activity

Please include the following labels on your poster:
  • Molten Rock
  • Mountains
  • Tectonic Plates
  • Mid-Ocean Ridge
  • Deep Ocean Trench
  • Volcano
  • Divergent Boundary
  • Convergent Boundary
  • Subduction Zone

The Theory of Plate Tectonics

A Canadian scientist, J. Tuzo Wilson, observed that there are cracks in the continents similar to those found on the ocean floor.

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In 1965, Wilson proposed the idea that the lithosphere was broken into separate pieces called plates.
Wilson combined what scientists knew about continental drift and sea-floor spreading into a single theory.
The Theory of Plate Tectonics states that pieces of the Earth's lithosphere are in slow, constant motion, driven by convection currents in the mantle. This theory explains the formation, movement & subduction of the Earth's plates.

As the plates move they collide, pull apart, or grind past each other to create all kinds of changes on the Earth's surface.
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Plate boundaries are where the Earth's plates meet. These boundaries go deep into the lithosphere. Faults - breaks in the Earth's crust where rocks have slipped past each other - form at these boundaries.

There are 2 kinds of plates:
  1. Oceanic - plates below the ocean floor
  2. Continental - plates below the continents

There are 3 kinds of plate boundaries:
  1. Divergent
  2. Convergent
  3. Transform

Divergent Boundaries

A place where two plates move apart.

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Most occur at the mid-ocean ridge.

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When these boundaries are found on land the Earth's land slides apart and deep valleys called Rift Valleys are formed.
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Africa's Great Rift Valley is an example
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As the land pulls apart, magma can rise up and volcanoes can form.
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Convergent Boundaries

A place where the plates come together. Two plates collide. When this happens the density of the plate determines what will happen.
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Oceanic and Oceanic
When two oceanic plates collide, the more dense plate will sink below the less dense plate. Volcanoes can be found here in a formation called a Volcanic Island Arc.

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Oceanic and Continental
When oceanic and continental plates collide, the more dense oceanic plate will sink below the continental plate. Volcanoes can be found along this plate boundary.
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Continental and Continental
When continental plates collide the land crumples up to form mountains. These are not volcanic.

Continental plates in motions
Continental - Continental in motion

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Himalayan Mountains are a great example of Continental Convergent Boundaries.
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Transform Boundaries

A place where two plates slide past each other.
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Boundary Interactive

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Major Volcano Map - Ring of Fire

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Major Earthquake Map

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Sea-Floor Spreading

In the Mid-1900's scientists started using sonar to map the ocean floor. They soon discovered large mountain chains underwater. These mountains became known as the Mid-Ocean Ridges.

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These mid-ocean are found in all of the oceans.
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Most of these mountains are hidden under the ocean water, but in a few places these mountains are so tall they rise above the ocean's waters. Iceland is an example of this.

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In 1960, Harry Hess, an American geologist, carefully studies the mid-ocean ridge mountains. Hess then began to re-evaluate Alfred Wegener's idea of Continental Drift and decided that perhaps the continents are really moving! Hess proposed a radical idea called Sea-floor spreading. He proposed that at the mid-ocean ridge magma was rising from the mantle and pushing the sea floor apart. The sea floor would spread along both sides of the mid-ocean ridge as new crust is added in the middle. The result is that the ocean floor is moving away from the mid-ocean ridges like a conveyor belt, carrying the continents with them.

Sea-floor spreading in Motion

Harry Hess found several pieces of evidence to support his idea.
1. Evidence from molten material.
  • Scientists dived to the ocean floor in a small submarine to explore the mid-ocean ridge. There they found pillow shaped rocks that are only formed from molten material that cools quickly underwater.
2. Evidence from Magnetic stripes
  • Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized "stripes". Basalt on the ocean floor contains iron. When the magma rose up from underground the iron lined up with the Earth's magnetic poles. When the Earth's magnetic poles reversed, so did the direction the iron lines up in the rock. This left a permanent record of the Earth's magnetic field changes.
3. Evidence from drilling samples
  • A drilling ship took core samples of the ocean floor. From these core samples scientists could age the rock. The youngest rock is near the mid-ocean ridges and the oldest rocks are near the plate boundaries.

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If the ocean floor is expanding, does that mean that the oceans will keep getting wider & wider?

The answer is NO. The ocean floor bends back down into the mantle at deep underwater canyons called deep-ocean trenches. Here, over millions of years part of the ocean floor will sink back down into the mantle.

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The process of the ocean floor sinking back into the mantle is called subduction. Sea-floor spreading and subduction work together. As new molten rock rises at mid-ocean ridges it is hot and less dense than surrounding rock. As the rock moves away from the mid-ocean ridge and cools down it becomes more dense and eventually sinks back down into the mantle at the deep-ocean trench.

Subduction in Motion

The process of sea-floor spreading changes the size and shape of the oceans. Right now the Atlantic Ocean is expanding while the Pacific Ocean is shrinking. This is due to the location of the subduction zones.
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Continental Drift

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Hypothesis proposed by Alfred Wegener (1910) says all the continents were once joined together in a single landmass called Pangaea.
He proposed that the continents slowly move over the Earth's surface. This idea was known as Continental Drift.

  • The Earth looks like a whole bunch of puzzle pieces. These pieces fit together
  • Fossils - Tropical plants were found in Arctic areas, freshwater reptiles found spread across salt water areas, warm land animals found spread out and in arctic areas, coal beds
  • Land Features - Folded mountains along South America & Africa
  • Climate - Glacier scratches spread across continents

Unfortunately, Wegener's Hypothesis was rejected because he could not provide a satisfactory explanation for the force that pushes or pulls the continents. In order for scientists to accept this idea they would need to change all their current ideas on how the world worked.

Continental Drift
Continental Drift - Pangea
Continental Drift Puzzle
Video - Discovery Learning (username: tb03bps & password: goblue)

Convection Currents

Convection & Movement of the Crust
Convection in the Mantle

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Our Magnetic Eath

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The Earth as a Magnet
Will the Earth's magnetic field flip?

How a compass works

The Magnetic Compass

Layers of the Earth

Earth's Interior Poster Directions

Inside the Earth Extra Credit Story

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Geologist's Notebook: Digging Through the Earth (United Streaming) Video

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