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Sci 7- Topics 4-5-6 Planet Earth
Transcript of Sci 7- Topics 4-5-6 Planet Earth
- primary waves are bent or refracted as they travel (the area where they do not come through the other side of the earth is called a shadow zone - Figure 5.52, p. 398) Locating an Earthquake - the surface waves come from the epicentre (the location on the surface directly above the focus) Earthquake Zones Types of Rock Movement in Earthquakes - stabilize furniture, storage of heavier items close to the floor, earthquake-resistant designs (allow building to bend a little) - tsunamis (Japanese word meaning 'harbour wave') are huge waves that happen when an earthquake occurs under the ocean
- avalanches or rock slides occur in mountains as a result of an earthquake
- type of foundation upon which building are constructed can have an effect on the severity of the earthquake (liquification) LA earthquakes 2:38 Aerial Footage of Christchurch NZ after Earthquake seismic waves 1:40 min focus-rock under the surface breaks,creating an earthquake
epicenter-point directly above the surface
seismic waves-carries energy released in an earthquake
P waves-waves that squeeze and stretch the Earth
S waves-waves that move from side-to-side as well as up-and-down
Surface waves-waves that move like ocean waves
seismograph-records ground movements caused by seismic waves
magnitude-measurement of Earthquake strength
Richter scale-rating of how big a seismic wave is
moment magnetude scale-rates total energy of an earthquake Other Effects of Earthquakes - the zones of greatest intensity (8 or more on the Richter scale) 1 off Canada's west coast, 8 in Mexico, and 8 in Alaska - Animals: rabbits hop wildly for several minutes, deep-sea fish swim close to the surface, catfish jump out of the water, bees evacuate their hives, and mice are dazed before an earthquake DID YOU KNOW? Preparing for Earthquakes - scientists called seismologists use a seismograph to record the intensity of an earthquake - the seismograph must be attached to bedrock (the solid rock that lies beneath the soil and looser rocks) to feel the vibrations on the plate - a marking pen, inside the seismograph, records the vibrations on a rotating drum (modern seismographs are electronic) - seismic waves are the energy waves that travel outward from the source of the earthquake. Primary or p waves are the fastest and can push through solids, liquids and gases
Secondary or s waves travel more slowly and can only pass through solids - it is possible to determine the location of an earthquake by the interval between the p waves and the s waves (the farther apart they are, the further away the earthquake is) - the source of an earthquake deep in the crust is called the focus, where the p waves and s waves originate (shear causes slipping, which makes the jagged edges break off) - Pacific Plate - where the plates meet, the rock is under great pressure, which can make it bend and stretch - when the pressure is too great, the rock breaks suddenly creating a fault - there are three types of movement, of the tectonic plates, along a fault (see Figure 5.54, p. 403): Do you know these terms by now? Page 401. Use the graphs to analyse the first 3 questions Page 402 Handout.
Plot out the focus of each
erathquake Read page 404.
look at the building in Vancouver
what do you think? TOPIC 5 REVIEW
Questions 1-4 A volcano is an opening in the Earth's crust that releases lava, steam and ash when it erupts (becomes active). The openings are called vents. Current Volcano update: - volcanoes that form a circle around the Pacific Ocean are called the Ring of Fire (derived from the circle of volcanoes that pour out red hot lava, fire and steam) - those on Mars and our moon have been extinct for millions of years, while those on Venus may still be erupting
- the largest volcano found in our universe is the extinct Olympus Mons on Mars DID YOU KNOW... Topic 6- Volcanoes Famous Volcanoes Remember the news about that volcano in iceland? It put out so much ash that europe airports were closed for weeks 1 min on vents Krakatau Erupts on Home video A trek on a Dormant Volcano turn down the volume- loud video shows that volcanoes cannot be predicted and don't always behave in ways scientists think they will behave. They can be rather spectacular. - the eruption of Mt. Etna in Italy - the most active volcano on the Earth is Kilauea in Hawaii Loud vid- turn down (blast was heard 4800km away and tsunamis waves were 30 m high) - Krakatau, in Indonesia this video is one of Kakataus many eruptions, they happen often. The size of the eruption in 1983 was close to 80 times bigger than this video. - Mount St. Helens, in Washinton (sideways and vertical eruptions) take out your map of the world.
turn to page 408-409.
locate the volcanoes and earthquakes on your map. Your first three marks should look like this... . . . Homework:
on page 411-
Review questions 1-4 More Visuals Earth's Layers 1 min Earth's Core 2:38 So what does the Earth's Core do? Videos are loud!! turn down!! Can you name the parts of the earth? Alfred Wegener was a scientist who believed that the continents were once all together. he collected evidence to explain the various shapes of the continents and how they were all together at one time. continental drift 2mins plants
climate Shapes estimated plates in 2 mins The Visuals 2:22 min (compression, where rocks are squeezed, causing them to bend and break) - Marianas Trench, near Japan (pulling action, which breaks rocks apart) - North Atlantic Normal Faults, Reverse Faults Strike-Slip Vocabulary When volcanoes are not active, they are called dormant. Mark each one. - Mount Vesuvius, in southern Italy (City of Pompeii was buried - it is due for another large eruption because it is sealed with a 'rock plug' that could blast 1.5 km upwards)
- Mount Pinatubo, in the Phillipines (ash circled the globe and cooled temperatures around the world) 1880-1930