The Processes That Have ShapedPlanet Earth

Mr. Bradford

How Do We Get

The Earth’s Magnificent

Features?

How The Earth Formed

• The Earth formed from the same dust cloud that formed the sun.

• As the dust circled around the sun it clumped and began to grow.

How The Earth Formed• Soon a proto-planet formed that swept up the remaining dust

and particles in its path.

The Early Earth• The beginning of Earth was marked with volcanic action and

bombardment from meteors.

• Meteors added essential elements crucial for life.

The Early Earth• After a while the Earth cooled, an atmosphere formed and the

crust solidified.

• Volcanic (outgassing) activity contributed to the atmosphere.

• Comets and Meteors

contributed the the water

on Earth.

What is the Earth Made Of ?Composition of Earth's Atmosphere• Nitrogen 78.1%

• Oxygen 20.9%

• Argon 0.9%

• Carbon dioxide, Methane,

Rare (inert) gases 0.1%

Composition of Earth

• Iron 32.1%

• Oxygen 30.1%

• Silicon 15.1%

• Magnesium 13.9%

• Sulfur 2.9%

• Nickel 1.8%

• Calcium 1.5%

• Aluminum 1.4%

• Other 1.2%

 

Earth’s Rocks• Igneous Rocks--formed when molten magma cools and are divided into two main categories: plutonic (intrusive) and volcanic (extrusive). Intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust (example granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta (examples pumice and basalt)

GranitePumice

Earth’s Rocks• Sedimentary Rock--For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly

turn into rock.

Earth’s Rocks• Metamorphic Rock--formed by subjecting any rock type to different temperature and pressure conditions than those in which the original rock was formed. These temperatures and pressures are always higher than those at the Earth's surface and must be sufficiently high so as to change the original minerals into other mineral types or else into other forms of the same minerals.

The Layers of the Earth

The Layers of the Earth• The inner core is solid iron

• The outer core is liquid iron

• The mantle is composed of iron (Fe), magnesium (Mg),

aluminum (Al), silicon (Si), and oxygen (O) silicate

compounds.

• The mantle is solid but is at a

temperature of 1000o C, so it

can deform slowly like hot plastic.

• The crust is composed of calcium

and sodium aluminum-

silicate minerals.

• The crust is thin, cool and brittle.

It can break and crack easily.

Convection• Something that is hot is less dense than something that is cool.

• More dense (cooler) things will tend to sink while less dense

(hotter) things will tend to rise.

Convection in the Earth• The convection process happens in the Earth as well.

• The cooler, denser crust will sink to the bottom, while the

hotter, less dense inner regions will rise to the top.

• When convection

happens on the Earth

it drives a process

known as

Plate Tectonics.

Plate Tectonics• The Earth’s crust is broken into different segments.

• These different segments are called plates.

• There are seven major plates.

• These plates move (slowly) over the earth, crashing and

grinding against each other.

Earth’s Plates

Continental Drift• In the past all the continents were one large continent

named Pangaea.

• Plate tectonics contributed to the breakup of Pangaea into the

continents we have today.

• The continents continue to move about 5 to 10 cm per year.

Effects of Plate Tectonics• Earthquakes happen when two plates rub against each other.

• Ridges form when two plates move apart from one another.

• Volcanoes and trenches other mountains form when two

plates

collide.

Earthquakes• The boundary where two plates rub against each other is called

a transform boundary.

• Earthquakes occur along

this boundary also

called a fault.

Earthquakes• San Andreas Fault, California

Ocean Ridges• Ocean ridges form when two plates pull apart from on another.

• This is known as a divergent boundary.

• Hot magma will rise up at this boundary, solidify, and form

underwater mountain ranges.

Ocean Ridges

Volcanoes• A convergent boundary

is where two plates

collide.

• When plated collide,

one plate usually gets

subducted, or pushed

beneath the other plate.

This is known as a subduction zone.

• Volcanoes and earthquakes form near these subduction zones.

Volcanoes

As the subducted plate sinks, it will grow hot, melt, and form magma which will rise under pressure and form an earthquake.

When the pressure grows strong enough it will erupt

Diagram of a Volcano

Mt. St. Helens Before May 18, 1980

Mt. St. Helens After May 18, 1980

Effects of Volcanoes on EarthVolcanic soil is ideal for plant growth.

Volcanoes added much needed water vapor to Earth’s atmosphere in the beginning.

Large eruptions can cause a mass extinction of plant and animal species. This happens mainly from the ash that lingers in the atmosphere for long periods of time, blocking the sun. Some of the poisonous gas will rain down in the form of acid rain.

Hot Spot VolcanoesHot Spot volcanoes are less violent than those near subduction zones.The crust slowly moves over a “hot spot”—an area of magma formation.The movement will create a string of volcanic islands that will cool and flourish with life.

The Hawaiian islands were formed

(and are still being formed) by a

hot spot volcano.

The Pacific Ring of Fire

MountainsMountains can form when two plates collide causing one or both plates to rise up.

Other Mountains are formed when a plate under pressure will swell, fold and fault.

Mountains—Folding and Faulting

Folding and Faulting

Mt. EverestMt. Everest is the highest mountain in the world. It is 29,028 ft. (5 ½ miles) high. Mt. Everest is part of the Himalayan mountain range which was formd when the the Indo-Australian plate collided with the Eurasian plate.

The Himalayas

Mountains

Other mountains are formed by the erosion of high plateau regions, leaving the harder parts standing above the surrounding area.

GlaciersA glacier forms when the annual snowfall exceeds the amount of snow and ice lost due to melting.Snow thus accumulates year after year. The snow at the bottom is compacted into ice (firn). Eventually the weight of the snow and ice becomes so large that the glacier begins to slowly fall (drift) downhill.The glacier carves a path in the landscape and leaves debris in behind.

Glaciers• Glaciers carve

mountains and

valleys

• Much of the shapes

we see in

mountain ranges

is a result of

glaciers.

Glaciers

Glaciers—Cirques Cirques—steep bowl-like depression carved in the side of a mountain by a glacier’s snow field.

Cirques

Cirques

Glaciers—Horns

Horn—a sharp, pointed peak carved by three or more opposing cirques cutting into the mountain.

Glaciers—Hanging Valleys

Hanging Valley—the intersection of two valleys which were carved by glaciers. One of the valleys is larger and deeper than the other. The smaller valley “falls into” or “hangs” over top of the larger valley.

Waterfalls often occur at these intersections.

Hanging Valley

Hanging Valley

Hanging Valley

Agents of Erosion

Erosion is the breaking down of a material.

Wind, Water and Chemicals are the main agents of erosion.

These also help carve out our Earth.

Wind ErosionWind will blow small debris (sand and other particles) that will carve out features in rocks, mountains and anything else in its path.

Water Erosion

Rain and rivers, over time, carve away at rocks.

Rivers will cut into the landscape and can form valleys and canyons over time.

Oceans constantly shape the shores and eat into cliffs.

Water Erosion

Water Erosion

Wind and Water

Chemical Erosion

Chemicals put into the atmosphere will come down in the form of acid rain and alter and destroy some landforms.

Other chemicals will seep into the ground and waters change the composition of their contents.

Other Types of Erosion

Water freezing in cracks and expanding

Roots of plants growing into crevasses and growing to the point that the crack or crevasse widens and breaks.

Human activity. Building, cutting down, blowing up, etc.

This Concludes My Presentation