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Mountains, Earthquakes, and Volcanoes

# Mountains, earthquakes, and volcanoes

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Mountains, Earthquakes,

and Volcanoes

Review

•Plate Tectonics – the big picture, creation of the major geographic features of the Earth

•Layers of the Earth•Plate Boundaries

Layers of the Earth

Do you know what this means?

S6E5. Students will investigate the scientific view of how the earth’s surface is formed.

c. Describe processes that change rocks and the surface of the earth.

Plate Boundaries

•3 Kinds of Plate Boundaries• Divergent• Convergent• Transform

•Are the result of “pulling” forces

•Have small earthquakes

•Create many normal faults

•Are usually on the opposite side of the plate from a convergent boundary

• Collision of two plates

• Have all the large earthquakes

• 90% of all earthquakes happen here

• Ocean-continent collisions = subduction

• Explosive volcanoes

• Reverse faults

•Are the result of parallel and opposite forces

•Have small to medium earthquakes

•Create strike-slip faults

•Can cause streams to turn at right angles

Stress Due mostly to plate movements, the earth’s crust is under a lot of stress. There are 3 types, shown at the right

o“A” occurs where plates pull apart, divergent boundaries, and is called tension

o“B” occurs where plates converge, and is called compression

o“C” occurs where plates move past each other, at transform fault boundaries and is called shearing

Strain • Stress leads to strain on the crust which bends it.

If it is warm, under the ground, it can bend. The features are called folds. • Upturned folds are

anticlines while downturned folds are synclines.

• Or the rock may break, if it is brittle. This causes faults –breaks of the earth.

anticline syncline

A fold above and a fault below

Different faults

Faults move in different ways, depending on the type of stress on them. Remember “3” types form. 1.Normal fault2.Strike slip fault3.Reverse fault

3

Can you match the stress and strain?

3

Geographical Features

•Mountains•Earthquakes•Volcanoes

Plate Tectonic and Mountain Formation

• The most common types of mountains:1. Folded Mountains: from when rock layers

are squeezed together and pushed upward –Ural Mountains (Russian)

2. Fault-Block Mountains: form when tension causes land to drop down – Teton Range (USA)

3. Volcanic Mountains: molten material rises to the Earth’s surface and erupts on the surface - Mount Kilimanjaro (Africa)

Mountain Formation

Mountains can be a result of:

1.Continental Collisions (Himalayan Mountains; Alps in Europe)

2.Volcanic Eruptions (Mount Kilimanjaro-Africa; Parícutin-Mexico)

3.Hot Spots (Mauna Kea- Hawaiian Islands)

4.Subduction Zones (Andes Mountains)

5.Sea-floor Spreading (Mt. Oraefajokull -Iceland: Mid-Atlantic Ridge)

Continent-Continent Continent-Continent CollisionCollision

When two (2) continental plates come together.

The plates push up and form mountains

(Example: Himalayas)

• When continental crust pushes against continental crust both sides of the convergent boundary have the same properties.

• Neither side of the boundary wants to sink

beneath the other side, and as a result the two plates push against each other and the crust buckles and cracks, pushing up (and down into the mantle), forming high mountain ranges.

• Examples: 1. The European Alps 2. Himalayan Mountains

Alps in Europe

Collision of Africa and Eurasia

HimalayasHimalayas

Andes Mountains in South AmericaAndes Mountains in South America

Interesting plate collisionInteresting plate collisionThis picture shows a place in Newfoundland where a massive collision actually forced mantle rock on top of the crust, during the collision that formed Pangaea and the Appalachian mountains. This looks down the old plate boundary.

SUBDUCTIONNazca Plate dives

under the South American Plate

Convergent: Ocean/ocean Japanese Islands

Volcanic Mountains

• A recent witnessed example of a volcano being born was the spectacular event that began on February 20, 1943, when a farmer's cornfield in Mexico suddenly began to erupt. By the second day, the cone had risen to 100 feet (30.5 m.). By two weeks it was 450 feet high (137 m.), and when the eruptions finally ceased in 1952 the cone had risen to 1,350 feet (411 m.).

Volcán de Parícutin

Basic Earthquake Facts

• Mostly happen along/on plate boundaries

• Seismographs can record earthquakes from all over the world

above 2.5-3 on magnitude scale

• Earthquakes are a release of energy

Earthquakes• Earthquake – The shaking and

trembling that results from the sudden movement of part of the Earth’s crust– Pebble in pond– Scientists predict over 1,000,000

earthquakes happen each year– Faulting is most common reason

for Earthquakes• San Andreas Fault

– Fault Video

http://youtu.be/ZxPTLmg0ZCw

Fukushima’s Earthquake• An earthquake shook Fukushima in

11th March 2011. It caused a tsunami.

• As a result of the earthquake and tsunami, there was an explosion in nuclear reactors.

http://youtu.be/qtCLlNFUhWk(stop at 3:10—coast before/after)

Tsunamis

• Also called tidal waves • Large ocean waves caused by an

earthquake under the ocean.• Ocean floor moves along a fault

creating a wave.• Can also be caused by a landslide

under or above the water.

Tsunamis• Remember this huge

wave is caused by an earthquake on the floor of the ocean– They can travel at speeds

of 700 to 800 MPH– They can reach Heights of

20 meters• The height of a 6 Story

Building• Tsunami Off of Thailand• Trouble in Paradise

Seismic Waves• Earthquake waves are

known as seismic waves– Focus- The point beneath

the Earth’s surface where rocks break and move

• The focus is the point of origin for the earthquake

– Epicenter- Directly above the focus on the Earth’s surface

• Earthquake waves reach the epicenter first

• Seismic Waves

Seismic Waves• Primary waves-

– “P-waves”: Seismic waves that travel the fastest

• They arrive at a given point before any other type of wave

• They travel through– Solids– Liquids– Gases

Seismic Waves• Primary waves-

– They move through the Earth differently depending on the material they are traveling through

– As they move deeper into the Earth, where it is more dense, they move faster

– They are push-pull waves

Seismic Waves• Secondary Waves

– S-Waves – Seismic waves that do not travel through the Earth as fast as P-waves do

– S-waves arrive at a given point after P-waves do– S-waves travel through solids but not liquids and

gases

Seismic Waves

• Surface WavesL-waves: They are the slowest moving seismic waves

• They arrive at a given point after P and S wavesThey start at the epicenter and move along the Earth’s

surfaceEarth’s surface moves up and down like water waves doThey cause the most damage to the Earth because they

bend and twist the surface

Seismograph• Seismograph – An

instrument that detects and measures seismic waves

– Consists of • A weight attached to a

spring or wire• A pen attached to the

weight that records the movement of the Earth on a paper, that is wound tightly around a constantly moving drum

• Seismologists – Scientists who study earthquakes– PSP Seismograph– They can determine the strength of

an earthquake by studying the height of the waves

• They look at a Seismogram• They match the seismogram to a chart

called the Richter Scale– Invented in 1935– The scale is from one to ten, with any

earthquake above 6 being very destructive

Seismograph

Earthquakes in the World

Earthquakes may cause::1. Destruction of homes

2. Destruction of infrastructure (roads, bridges)

3. Soil damage4. Landslides5. Tsunamis

These can also result from earthquake aftershocks

VolcanoesAn opening in the earth that erupts

gases, ash and lava.oCaused by plate movement along

boundaries.oOccur at both divergent and

convergent plate boundaries.

• Formation

• High temperature• High Pressure• Liquid State• Found in pockets called magma

chambers

– Magma constantly moves and works its way through cracks toward the surface by melting the solid rock

Volcanoes

–Magma: Rock deep within Earth

• Formation– Lava – Magma that has reached

the Earth’s Surface– The place where magma becomes

lava is called a Volcano– The opening through which lava

erupts is called a vent• Volcanoes can have more than one

vent– Lava will poor from the sides of a

volcano as well as the top

Volcanoes

Volcanoes

• All volcanoes form from an expulsion of materials from deep within the earth in the form of enormous amounts of lava or cinders which pile up on the earth's surface, forming a mountain.

MAGMA

• All are not Alike– Some are quiet

• Lava oozes from a vent

– Others are violent• With lava and other material hurled

hundreds of feet in the air• Gases and earth material mix to be seen

from miles away

– The opening through which lava erupts is called a vent

• Volcanoes can have more than one vent– Lava will poor from the sides of a

volcano as well as the top

– Eruption

Eruptions

Types of Volcanic Eruptions

Two factors determine the type of eruption: Amount of water vapor & other gases in the magma The chemical composition of the magma

Eruptions• During eruptions many rock fragments are blown

into the air– Smallest = volcanic dust– Medium = volcanic ash– Large = volcanic bombs

• Small volcanic bombs the size of golf balls are called Cinders

•Lahar (mudflow): mixture of ash, eroded land, and water flowing down river valleys

•Gases: water vapor, carbon dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, chlorine

Types ofVolcanoes

Different types of volcanic eruptions form different types of volcanoes

1.Cinder Cones - made mostly of cinders and other rock particles that have been blown into the air

– Form from explosive eruptions– Cones are not high– Narrow base & steep sides

2.Shield Volcanoes – composed of mostly quiet lava flows– Gently sloping, domed shaped mountain forms

3.Composite Volcanoes – Built up of alternating layers of rock particles and lava

– First is a violent eruption– Then a quiet eruption– After many alternating eruptions a cone shape is formed

Volcano Visuals• Shield – volcanic cone

made up of layers of hardened lava

• Cinder cone – volcanic cone made up of rock particles, dust and ash.

• Composite – volcanic cone made up of alternating layers of lava and rock particles.

Volcano Anatomy

Volcanoes• At the top of a funnel-shaped pit or

depression is a pit– Called Crater

• If it becomes to large it is called a Caldera• Super Eruption• Discovery Channel :: Virtual Super volcano

•Cone: the above ground structure built from lava and/or tephra

• Parasitic Cone: a smaller secondary volcano built on the side of or near the main volcano, but sharing the same conduit to the magma chamber

Fumarole: a secondary vent that emits only gases

•Conduit: the path that magma takes from the magma chamber to the vent

• FissureFissure: a long fissure : a long fissure (crack) from which lava flows(crack) from which lava flows

• Scientists study the makeup of the lava that spews from the volcanic vents to gain knowledge about the interior magma

• Types of Lava– Dark-colored/ Water– Light-colored/ little Water– Chemical composition of

both– Large amounts of gases

• Steam and carbon dioxide

Eruptions

3 Types of Lava

1.1. Pahoehoe lavaPahoehoe lava: :

Hot, thin, fast Hot, thin, fast flowing flowing

harden with a harden with a relatively smooth relatively smooth surface surface

Often has a ropy or Often has a ropy or wrinkled appearancewrinkled appearance

2. Aa lava:

Cooler, thicker, slow moving

Hardens with a rough, jagged, sharp edge surface

3. Pillow Lava:

Lava suddenly cooled by water

shows sack-like segments (stuffed pillows)

Ring of FireA chain of volcanoes located in the Pacific Ocean

Hot Spots• A part of the mantle is REALLY hot

and magma is forced up to the surface

• Creates islands. – (Example: Hawaiian Islands)

Magma that may originate in the mantle or outer core will move upward, breaking the surface and forming a volcano, they are independent of plate boundaries and a chain of volcanoes may form as the plate moves across a hot spot.

• Three Major Zones– Nearly all the way around the edge of the

Pacific Ocean• Called the Ring of Fire

– Near the Mediterranean Sea• Called the Mediterranean Zone

– Third Extends through Iceland to the middle of the Atlantic Ocean

• Mid-Atlantic Ridge – Long ridge of volcanoes

Zones

Volcano Activity Levels (Stages)

1. Active (awake): Has erupted within recent time and can erupt again at any time.

Pre-eruption activities: • Increase in earthquake activity under the

cone• increase in temperature of cone,• melting of ice/snow in the crater• swelling of the cone• steam eruptions• minor ash erupt

2. Dormant (sleeping):

•No eruption within recent times, but there is record of past eruptions •Can become active and erupt again after a “wake up” period •Example: Mt. Rainier

3. Extinct: No eruption within recorded

historyNot expected to ever erupt

againExample: Mount Mazama

(Crater Lake)

DIVERGENT BOUNDARY – move apart

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