Chapter 2 – A Tropical Alberta

1. Chapter 2 – A Tropical Alberta Pages 328 - 365

2. 2.1 – The Cambrian Explosion (pages 330 – 335)

3. Fossilization – the process by which any trace of the existence of ancient life is preserved within rock • The process of fossilization can be summarized: • Life  death  burial  preservation  discovery  recovery

4. Fossilization Process • Organism is buried before it decomposes • Hard parts (ie. shells and teeth) can be found in rock as unaltered remains • When original material is replaced by minerals, like silica, the resulting fossil is petrified

5. When hard parts disappear , the space left behind is called a mould • The impression on the outside of a hard part is called an external mould • The impression left on the inside is called an internal mould

6. Soft tissues (ie. leaves and skin) can be fossilized by the complete replacement of the organic material, with an impression of the organic material left behind • Soft parts can be preserved as a thin layer of carbon

7. Fossils are most often found in sedimentary rock because remains are usually buried in layers of sediment • Trace fossils contain no remains of actual organisms but are evidence of their existence – ie. stromatolites

8. Comparing Fossils and Modern Organisms • Fossils are often compared to living organisms because some information is not preserved in the fossil record

9. The Burgess Shale • Located in Yoho National Park • Most significant source of Cambrian fossils • Fossils age 525 - 545 million years old

11. Alberta’s Tropical Coastline • During the Cambrian Period it is suspected that all life is marine life • Alberta was positioned close to the Equator • Alberta was repeatedly submerged and lifted above the ocean’s surface

12. Burgess Fossilization Conditions • Believed that series of underwater mud avalanches buried deceased organisms in deep mud • Low oxygen environment in deep water • No scavengers • Preservation of Burgess fossils is very high quality

13. The Cambrian Explosion • The Cambrian Period marks the appearance of organisms with hard body parts like shells • ~ 20 million year time period (very short in geological time) • Biologists refer to this rapid diversification as an explosion • Almost all modern animal groups can trace origins to beginning of Cambrian Period

14. 2.1 Summary • Wealth of data from Burgess Shale provides insight into underwater ecosystem from 545 million years ago • Underwater mud avalanche helped create high quality fossils • During Cambrian explosion seeds are sown for the origin of nearly all modern groups of animals

15. 2.2 – A Billion Dollar Reef (pages 336 – 342) • Petroleum: liquid hydrocarbons formed over millions of years from the remains of ancient microscopic marine organisms • Leduc area is rich in petroleum deposits

16. Petroleum discovered at Leduc #1 in 1947

17. Ordovician Period: 440-500 million yrs ago • Follows Cambrian Period • Marks move from marine life to land • Earliest plant fossils date back 470 million years • Jawless fish first animal with backbone • Most of Alberta is submerged • Vast coral and sponge reefs in seas

18. Silurian Period: 410 – 440 millions yrs ago • Continued reef development • First land animals: scorpions, millipedes

19. Devonian Period: 360 – 410 million yrs ago • Apex of reef building • Accumulation of dead microscopic plankton stored at sea’s floor • Bacteria have removed oxygen from organic “ooze”, hydrogen and carbon are left behind (main components of petroleum)

20. How is Petroleum Formed? • Microscopic plankton die and sink to bottom of sea • Thick blanket of organic matter forms • Thousands of meters of sediments accumulate on top

21. Pressure from above pushes organic material into porous fossilized reefs • Impermeable rock above and below traps the petroleum (petroleum trap)

23. Petroleum is often trapped 1 km below surface • Drill core, subsurface rock sampled during drilling operations, is used to identify rock below surface • Fossils in drill core give insight into ancient environmental conditions • A detailed map of Alberta’s subterranean rock exists due to extensive drilling

25. Seismic waves: travel through Earth as a result of explosions or earthquakes • Seismic technology: • Uses explosives in “shot hole” • Use huge force to vibrate plate against surface of Earth

26. Seismic waves generated reflect off different densities at rock layer boundaries

27. Geophones convert seismic waves into electronic signal • Seismograph processes signal • Seismogram is a summary of the info • Suggests where petroleum traps are located • Only drilling can determine this for sure

30. 2.2 Summary • During the Ordovician, Silurian and Devonian Periods, Alberta is submerged under water • Dead remains of microscopic organisms created an thick organic layer • Thick layer was transformed into petroleum over millions of years • Petroleum is located by drilling cores and analyzing seismographs

31. 2.3 – Earthquakes (pages 343 – 351)

32. What Causes Earthquakes? • Potential energy builds up at the boundary two crustal plates (fault) as they move towards one other • If the two plates are different densities; the denser plate is pushed beneath the less dense plate (subduction)

33. The Process of Subduction • Fault – the boundary between crustal plates • Subduction – the process of a more dense crustal plate being pushed under a less dense crustal plate • Stress causes the upper plate to deform and store elastic potential energy • When the stress overcomes the breaking strength of the rock, a break occurs and the potential energy is released Subduction Animation

34. The sudden motion of the lithosphere causes seismic waves to be sent out • Energy is transferred to other points on the Earth’s surface • Focus – the area that first breaks along a fault • Epicentre – the point on Earth’s surface directly above the focus

35. Label the diagram with the following terms: fault, focus, epicentre, lithosphere, asthenosphere, seismic waves, oceanic crust, continental crust

36. Types of Seismic Waves • Energy is transferred from the focus to the surface through subsurface rock • Energy is transferred by seismic waves • 2 types of seismic waves • Primary waves (P-waves) • Secondary waves (S-waves)

37. P-Waves (primary waves) • Primary waves are the first to arrive because they travel the fastest • Travel through rock as matter is compressed and then expanded • Low frequency sound waves that can travel through solids, liquids, gases • Classified as a longitudinal (parallel) wave

38. S-Waves (secondary waves) • Slower than P-waves; can only move through solid rock • Rock vibrates up and down as the wave moves forward • S-waves have a larger amplitude (displacement) and transfer more energy • Classified as a transverse (perpendicular) wave

39. P-Waves, S-Waves, and Earth’s Interior • Seismic waves travel at different speeds as they pass through Earth’s interior • As depth increases, the speed of both P-waves and S-waves increases • What property of the Earth’s structure accounts for this observation?

40. Surface Waves • Surface waves do not travel through the interior of the Earth • Surface waves move along the surface of the Earth and cause the ground to move up and down and side to side • Waves travel slowly and do not travel far from epicentre

44. Determining the Location of the Epicentre • The time difference between the arrival of S-waves and P-waves provides a method of determining the distance between the sensory equipment and the epicentre • The farther away the epicentre, the greater the time difference between the arrival of the P-waves and S-waves

45. Calculate the speed of waves I, II, and III if 20 seconds have elapsed. What type of wave corresponds to each wave?

46. Richter Magnitude • The time interval between the two waves can also be used with other values to determine the Richter magnitude of an earthquake • Richter magnitude – a number assigned to an earthquake based upon the amount of vertical ground motion at its epicentre

47. Tsunami – a seismic sea wave set off by an earthquake in or near an ocean basin

48. 2.3 Summary • Earthquakes occur because of the sudden release of energy • Potential energy builds up over time due to the movement of crustal plates • Sudden release of tension causes seismic waves to move through surrounding rock

49. 2.3 Summary • Seismic waves: • P-waves – very fast, longitudinal; solid, liquid, or gas medium • S-waves – slower; transverse, solid medium • Surface waves – slowest, surface wave, mainly solid medium

50. 2.3 Summary • The difference in arrival times of P-waves and S-waves can be used to determine distance to epicentre • Information can also be combined with amplitude info to determine the Richter magnitude of the earthquake