Science Lesson

• Continental Drift Hypothesis


  Proposes that the continents were assembled to form the super continent Pangaea

  Moved Through Time
• Continental Drift Theory


  Alfred Wegener believed landmasses of Earth once fit together to form single landmass called "Pangaea"; landmasses "drifted" to where they are today; theory disregarded due to lack of evidence
• Alfred Wegener


  Proposed the continental drift theory in the 1900s
• Fit of Continents


  Antonio Snider-Pelligrini (1858) a geographer cut out a map of Africa and south america suggesting they were connected at one time

  Other Physical evidence based on observation was used by Wegener
• Fossil Evidence


  Similar terrestrial species were found on many continents now separated by oceans

  Information collected by paleontologists
• Ancient Mountain Ranges


  The same sequence of rocks is found in North America, Great Britain, and Norway. The pattern does not make sense with the continents in their current configuration
• Evidence of Ancient Glaciers

  Glaciers carve rocks as they move

  Scientists can determine the direction of movement (notice the direction of movement noted in South America)

  As South America sits today, the pattern would not make sense. (glaciers do not move from sea level to higher elevations
• Lacks of mechanism to explain continental movement

  Evidence implied that the continents were at one time assembled

  Wegner's idea was not accepted by the scientific community because he could not explain how the continents moved

  With advances in technology, new information was gathered in association with WWII
• Exploration of the Ocean Basins

  Seafloor features

  Composition of the seafloor

  Age of the seafloor

  Hot spots

  Seismicity

  Paleo-magnetic pattern produced on the seafloor
• Sonar


  Used to discover seafloor features
• Echo Sounding


  Used to map the seafloor
• Seafloor features


  Mid-oceanic ridges

  Trenches

  Volcanism adjacent to trenches

  Seamounts

  Fracture zones
• Seafloor Spreading


  Mafic lava is extruded along the mid-oceanic ridge to produce ocean floor

  New material is added, the cooler material is split and is "pushed" away from the ridge
• Mafic lava


  dark-colored lava rich in magnesium and iron
• Drive Mechanisms


  Convection cells within the mantle

  Pushing at the mid-oceanic ridges

  Pulling at the subduction zones
• Plate boundaries


  divergent, convergent, transform
• Divergent Boundary


  variant, moving apart
• Convergent Boundary


  A plate boundary where two plates move toward each other.
• Transform Boundary


  A plate boundary where two plates move past each other in opposite directions
• plate boundaries


  divergent, convergent, transform
• continental boundary


  the boundary between two continental plates
• oceanic boundary


  A boundary that is covered by ocean water.
• 3 Types of earthquake

  Shallow Fault Earthquake

  Subduction Earthquake

  Deep Earthquake
• Shallow Fault Earthquakes


  This is a type of earthquake that breaks the rock beneath our feet. Shallow fault quakes occur very close to the surface.Shallow fault earthquakes are so near the surface, even smalls one causes a lot of damage from shaking.
• Subduction Zone Earthquake


  The largest earthquake ever recorded are subduction zone earthquakes. They can last several minutes. Subduction zone shaking can occur along the whole subduction zone.In the Pacific Northwest, these major earthquakes seem to occur every few hundred years.

  The last known subduction zone earthquakes along the Oregon and Washington coast was January 26,1700. In addition to causing huge shifts in land level here, this quake sent huge waves and tsunamis racing across the pacific.
• Deep Earthquakes


  It occurs in the sub-ducting ocean slab, deep beneath the continental crust. In the Pacific Northwest, deep quakes start about 50 km (30 mi) beneath the surface. Large ones have shaked the Pacific Northwest in 1949, 1965 and 2001 about every 30 years. The last big deep quake, the 2001 Nisqually earthquake occurred under the southern end of Puget sound
• Causes of Earthquake


  Earthquakes are caused by sudden tectonic movements in the Earth's crust.

  The continuous motion of tectonic plates causes a steady build-up of pressure in the rock strata on both sides of a fault until the stress is sufficiently great that it is released in a sudden, jerky movement.

  The resulting waves of seismic energy propagate through the ground and over the its surface, causing the shaking we perceive as earthquakes.
• 3 Causes of Earthquake

  Induced Seismicity

  Volcanic Tectonic Earthquakes

  Fault Movement
• Induced Seismicity


  It refers to typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on the Earth's crust.

  Most induced seismicity is of a low magnitude. A few sites regular have larger quakes, such as The Geysers geothermal plant in California which averaged two M4 events and 15 M3 events every year from 2004 to 2009.
• Volcanic Tectonic Earthquakes


  It is an earthquake caused by movement of magma beneath the surface of the Earth.

  The movement results in pressure changes where the rock around the magma has experienced stress. At some point, this stress can cause the rock to break or move.
• Fault Movement


  It is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movement.

  Large faults within the Earth's crust result from the action of plate tectonic forces, with the largest forming boundaries between the plates, such as subduction zones or transform fault.
• Volume Changes


  - Underground injection or removal of fluids or gases results in changes to the volume in the interstitial spaces of the rock. The change in volume, in turn, affects the tension, which may lead to new fractures or to the reactivation of existing ones.
• Increase of Pore Pressure


  - Water that enters the ground artificially or naturally increases the pressure in the pores of the rock. This decreases the infernal friction in the rock, sometimes leading to abrupt shifts along existing rupture surfaces.
• Chemical Changes


  - Chemical agents, such as acids, are often used in geothermal energy production and in fracking to increase the water permeability of the rock. Due to the dissolution and deposition caused by the introduction of the chemicals, the rock's normal volume and tension is altered, thus leading to a change in rock friction. If rock friction is reduced, naturally built-up tension tends to be released.
• Thermo-elastic Deformation


  - In geothermal energy production, cold water is injected into the rock, where it heats up, and is then transported back to the surface. A side effect of this is that the surrounding rock cools and contracts. The resulting stresses can lead to shifts in existing fractures.
• Load Change

  - Large load changes on the surface, such as those that arise during filling of a reservoir, can lead to changes in tension at depth. Under certain conditions, this triggers a reactivation of existing disturbances or causes new fractures in the rock.
• Precautions before an earthquake

  1.Make sure you have an emergency kit

  -Examples of these would be a first aid kit, bottled water, food (nonperishable),essential medicine, clothing, important documents.

  
  

  2.Secure heavy furniture

  -Put the objects in the lower shelves to prevent it from falling.

  3. Keep a list of emergency numbers

  -Just in case there is an earthquake and you or a family member gets harmed you have an emergency number to call immediately

  
  

  4. Learn how to use first aid kits, switching off the waterlines or gas tanks.

  -Just in case someone gets injured you can use the first aid kit. If no one else is around at least you know how to turn off the gas tanks or waterlines.
• Precautions During an Earthquake (Indoor)


  1.Drop, Cover and Hold

  -As much as possible just stay under a sturdy furniture.

  -If you are not near any sturdy furniture as much as possible cover your head and torso.

  
  

  2. Stay indoors until shaking stops

  - If in a building use the stairs instead of the elevator just in case there would be an after shock or power outage.

  
  

  3.Before you leave the building check the area

  -Check if there is anything that could possibly fall on you while you go out.

  
  

  4.If you smell gas, get out of the house as quick as possible

  -This is to avoid any fire hazard
• Precautions During an Earthquake (Outdoor)


  1.Find a clear spot to go to and drop to the ground until the shaking stops

  -Its better to be in a clear area to avoid trees or power outlines

  
  

  2. If in a vehicle pull over to the a clear area.

  -Avoid stopping at a bridge or overpasses.

  -Stay inside the vehicle with your seat belt fastened until the shaking stops.

  -When the shaking stops, drive on until you get to a safer area but avoid bridges or ramps that could be damaged.

  3. If a power line falls on your vehicle, do not go out and wait for assistance.

  -This is to avoid getting electrocuted

  
  

  4.If you are in a mountainous area be alert for falling rocks or landslides.
• Precautions After an Earthquake


  1.If away from home, return only when authorities say that it is safe to go back.

  
  

  2.Check yourself if you have any injuries then get first aid before helping injured or trapped people.

  
  

  3.Be prepared when there is an aftershock, landslide or a tsunami.

  
  

  4. Every time you feel an after shock you drop, cover and hold.

  
  

  5. Extinguish small fires that are near you

  -This is to avoid the fire to become larger and become even more hazardous.