• 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
Due mostly to platemovements, the earth’s crust Stressis under a lot of stress. Thereare 3 types, shown at therighto“A” occurs where plates pullapart, divergent boundaries,and is called tensiono“B” occurs where platesconverge, and is calledcompressiono“C” occurs where plates movepast each other, at transformfault boundaries and is calledshearing
Strain • Stress leads to strain on the crust which bends it. anticline syncline If it is warm, under the ground, it can bend. The features are calledA fold above and a fault below folds. • Upturned folds are anticlines while downturned folds are synclines. • Or the rock may break, if it is brittle. This
Different faultsFaults move in differentways, depending on thetype of stress on them.Remember “3” typesform.1.Normal fault2.Strike slip fault3.Reverse fault 3
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 FormationMountains can be a result of:1.Continental Collisions (HimalayanMountains; 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 Collision 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
Interesting plate collision This 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.
SUBDUCTION Nazca Plate dives under the South American Plate
Volcanic Mountains Volcán de Parícutin• A recent witnessed example of a volcano being born was the spectacular event that began on February 20, 1943, when a farmers 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.).
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 Waves L-waves: They are the slowest moving seismic waves • They arrive at a given point after P and S waves They start at the epicenter and move along the Earth’s surface Earth’s surface moves up and down like water waves do They 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
Seismograph• 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
Earthquakes may cause: : 1. Destruction of homes 2. Destruction of infrastructure (roads, bridges) 3. Soil damage 4. Landslides 5. TsunamisThese can also resultfrom earthquakeaftershocks
Volcanoes An opening in the earth that erupts gases, ash and lava. o Caused by plate movement along boundaries. o Occur at both divergent and convergent plate boundaries.
Volcanoes• Formation –Magma: Rock deep within Earth • 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• 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• 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 earths surface, forming a mountain. MAGMA
Eruptions• 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
Types of Volcanic EruptionsTwo factorsdetermine the typeof eruption:Amount of watervapor & other gasesin the magmaThe chemicalcomposition of themagma
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
Types of VolcanoesDifferent types of volcanic eruptions form different types ofvolcanoes1.Cinder Cones - made mostly of cinders and other rockparticles that have been blown into the air – Form from explosive eruptions – Cones are not high – Narrow base & steep sides1.Shield Volcanoes – composed of mostly quiet lava flows – Gently sloping, domed shaped mountain forms1.Composite Volcanoes – Built up of alternating layers of rock particlesand 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.
• Conduit: the path that magma takes from the magma chamber to the vent
• Fissure: a long fissure (crack) from which lava flows
Eruptions • 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
3 Types of Lava1. Pahoehoe lava: Hot, thin, fast flowing harden with a relatively smooth surface Often has a ropy or wrinkled 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 themantle or outer core will moveupward, breaking the surface andforming a volcano, they areindependent of plate boundaries and achain of volcanoes may form as theplate moves across a hot spot.
Zones• 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
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, butthere is record of past eruptions•Can become active and erupt againafter a “wake up” period•Example: Mt. Rainier
3. Extinct: No eruption within recorded history Not expected to ever erupt again Example: Mount Mazama (Crater Lake)