1. Week 7 Cretaceous and Snowball Earth

2. Past climates – why bother?

3. Cretaceous What was it like? How did the geography differ?
How can we assess past climates
What caused the climate to be so different?

4. What do we know about the Cretaceous?
From the BGS – landscape in the Cretaceous

5. Some context Billion = thousand million = 1,000,000,000 = 1 x 109
Earth is 4.54 billion years old
Life started around 3.8 billion years
Early man Homo habilis evolved around 2 million years

6. 6

7. Greenhouse and icehouse

8. Cretaceous
Starts: 150 Million years ago Ends: 65 million years ago

9. Chicxulub
10 km wide
Crater 100 km across
12 km deep

10. Late Jurassic/early Cretaceous geography

11. Late Cretaceous geography

12. Movement of the continents

13. Plate tectonics video
Iain Stewart

14. Carbon cycle

16. Ocean currents

17. What was the Cretaceous climate like?
Early Cretaceous in China

18. Cretaceous land masses
Paul’s Paleopages

19. Evidence from the Arctic

20. Arctic today

21. San Joachim Delta - California
The Sacramento-San Joaquin Delta is a region where two of California's largest rivers meet. Freshwater from the rivers mingles with saltwater from the Pacific Ocean, creating the West Coast’s largest estuary. Composed of 57 leveed island tracts and 700 miles of sloughs and winding channels, the Delta is a unique blend of small town communities, busy ship ports, farmlands, industries, highways, historical sites, and marinas.
When first explored by the Spanish in the 1770s, the Delta was a vast marsh covered with tules and teeming with wildlife. Settlers, mostly unsuccessful Forty-niners, began farming the region shortly after the start of the Gold Rush. To reclaim the land from swamplike conditions, they began to build levees. The levees were raised and strengthened over time and now protect islands whose surface can be 20 feet or more below the outside water level.
Today, the Delta is the hub of the State’s water distribution system. About two-thirds of all Californians and millions of acres of irrigated farmland rely on the Delta for water from the State Water Project and federal Central Valley Project. Delta water is vital to California’s economy, fifth largest in the world, and its growing population, expected to reach 53 million by 2030 (Department of Finance).

22. Cretaceous - dinosaur weather
3 July 2015

23. Rain

24. No Mount Everest

25. Swamps, mires, bogs

26. Arid Equator, no rainforests

27. Cretaceous flora and fauna

28. How can we assess the climate in the past?

29. Proxies for climate - fossils

30. Nilssonia

31. Modern cycad

32. First flowering plant: Archaeofructus

33. Hadrosaur footprints
Hadrosaur footprints

34. Polar light regime

35. Warm shallow seas
Rudists

36. Raised coral reefs – Huon Peninsula

37. Proxies for climate – volcanic activity

38. Mount Pinatubo Eruption 1991.
The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulfur dioxide to sulfuric acid, which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth's lower atmosphere or troposphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The climactic eruption of Mount Pinatubo on June 15, 1991, was one of the largest eruptions of the twentieth century and injected a 20- million ton (metric scale) sulfur dioxide cloud into the stratosphere at an altitude of more than 20 miles. The Pinatubo cloud was the largest sulfur dioxide cloud ever observed in the stratosphere since the beginning of such observations by satellites in It caused what is believed to be the largest aerosol disturbance of the stratosphere in the twentieth century, though probably smaller than the disturbances from eruptions of Krakatau in 1883 and Tambora in Consequently, it was a standout in its climate impact and cooled the Earth's surface for three years following the eruption, by as much as 1.3 degrees at the height of the impact. Sulfur dioxide from the large Laki fissure eruption in Iceland caused regional cooling of Europe and North America by similar amounts for similar periods of time. 38 38 38

39. Gases emitted by volcanoes

40. Greenhouse gases Water Carbon dioxide Methane Ozone Nitrous oxide (NO)
Chlorofluorocarbon (CFC)
Hydrofluorocarbon (HFC) 40 40

41. Sulfur Dioxide

42. Flood basalts

43. Deccan Traps
Trapp derives from Scandinavian “stairs”

44. Cretaceous Warmest period in Earth’s history
High levels of CO2 – intense volcanic activity
Different geography
Fossils of warm adapted animals and plants
A few degrees at Equator but 20 degrees C North Pole and degrees 40 C at South Pole
No icecaps 44

45. Snowball Earth 45

46. Joe Kirschvink http://www.snowballearth.org/

47. Snowball Earth Hypothesis – not all scientists agree
Planet Earth covered by ice from pole to pole
Milankovitch cycles – variations in axis and orbit
Low levels of greenhouse gases
Position of continents
Positive feedback mechanism
Joe was born and raised in the Southwest United States, which does not necessarily explain his infatuation with geology and biology, but it helps. Rather than attending an undergraduate university on the East Coast, where all of the rocks are covered with green goo, Joe chose to pursue his undergraduate education in Pasadena, California, where the atmosphere itself in the early 1970s was capable of cleaning the rock surfaces to show the beautiful geology underneath. However, upon the advice of two mentors (one with his magnetic mind in the stars, and the other more mindful of the magnetic minerals made by microbes), he reluctantly agreed to serve time in the East among the Ivy leaves at Princeton for his Ph.D. Joe did this, however, by traveling through Australia for a year (he recently went back, and is shown here standing on the Hamersly banded iron formation), and by spending about 50% of this time as a graduate student somewhere "in the field". He abandoned his experiment with the East Coast in 1981, and has been on the faculty back at Caltech ever since.
Joe has a lot of fun creating "nutty" ideas like the snowball Earth, and confusing paleontologists by trying to convince them that the Cambrian explosion was caused by a series of interchange events in the orthonormal Eigenvectors of Earth's Moment of Inertia Tensor. (A good number of paleontologists actually know what a tensor is, and realize that a moment of inertia is not just what keeps them in bed in the morning �.) Joe even pretends that animals can predict earthquakes, just to keep his seismological colleagues on their toes. His major claim to being a paleontologist is his prediction and discovery of magnetofossils, which are not very useful for biostratigraphy but are wonderful as a Martian biomarker and for increasing the NASA Astrobiology budget.
Joe likes to swim and ski, and to explore the hot mineral waters produced by Mother Earth. He is married to a neurobiological electron microscopist, Atsuko Kobayashi, and they have two children (Jiseki and Koseki), whose names mean "magnetite" and "gemstone" respectively in Japanese. As a result, the children will probably grow up to be bloodsucking lawyers. And his family still doesn't know if home is in Pasadena or Osaka. 47

48. What evidence might we look for to confirm the Snowball Earth theory?

49. Traces of glacial rocks

51. Glacial striations

52. Distribution of glacial rocks

53. Calculating CO2 Estimates of weathering River run-off Land elevation
Biological activity
Volcanic activity
Tested against geological sources from ice cores

54. Milankovitch cycles
Wobbles in axis and orbit
Axial precession
Apsidal precession

55. Albedo

56. Positive feedback

57. Weathering

58. Where will it rain most?

59. Where will it rain most?

60. Key ingredient for weathering

61. Silicate weathering
Silicate rock + Carbon Dioxide + Water Calcium ions + Hydrogen carbonate + Silicon Dioxide

62. What ended Snowball Earth?

63. Increased biodiversity

64. Cambrian explosion

65. Why study past climates?

68. Earth’s energy balance

69. What is energy?

70. Energy definition You can’t see it You know when it’s there (or not)
It can’t be created or destroyed
It can change from one form to another
Energy is a physical property
It’s a measure of the ability of the object to “make things happen”

71. Energy

72. Energy From the sun 1.74 x1017 Watts
Human population 100 Watts per person
1.0 x 1011
Energy from the sun is million times higher

73. Week 6 Past Climates

74. Checking for reliability
Where does the information come from?
Where was it published?
When was it published?
Does the author or publication have an agenda?
Are there references?
Where can you get more information? 74 74

76. Greenhouse and icehouse

77. Plate tectonics