1. How do you explain the presence of large boulders?
Spend a minute or two for their ideas; if they say “glaciers” ask them for evidence
This would be a radical scientific idea 150 years ago.

2. What natural factors have influenced Global Climate Change in the past?
Are ice ages natural? Will they change again? Are they anthropogenic or natural?

3. How do we know the climate of the past if we were not there to collect direct evidence?

4. Think like a scientist:
You have a good understanding of the relative age of sediment layers and rock features
Law of Superposition
You have a good understanding of the use of oxygen isotopes in estimating paleotemperatures from ice cores
What other evidence do have to support past glaciations?
What evidence would you have had 200 years ago?

5. How do you explain the presence of large boulders?
Spend a minute or two for their ideas; if they say “glaciers” ask them for evidence
This would be a radical scientific idea 150 years ago.

6. Louis Agassiz 1830s Glacial erratic
Generated a hypothesis: looking at the Alps, he hypothesized that glaciers used to cover much of Europe. Evidence: erratics matched rocks higher in mountains, striations; took decades to convince peers that were not in the same area he was
Not the only one working on this
Alpine glacier used to extend further down the valleys than today
Mountain glaciers had once been much thicker
Glacial erratic
The glacial striations in a representation of Agassiz's work
Etudes sur les glaciers of 1840.

7. HMS Challenger Expedition Crew – 243 Scientists – 6
Expedition Crew – 243
Scientists – 6
Duration of Expedition - 4 years
Distance sailed - 68,890mi
Number of sampling stations - 362
Number of depth soundings made - 492
Number of dredges taken - 133
Number of new species of animals & plants discovered - 4,700
Observations: Global study, ocean dredge, water temps, 50 volume report; key observation: fossils of sea animals were different in cold vs warm areas some what like biomes. No one had seen this before
Look at layers of a strat column, record of ocean temperature
Chemical laboratory onboard the ship

8. Milutin Milankovitch orbital parameters
Generated a hypothesis: changes in orbital parameters forces Earth’s climate/temperature to change
Spent 30 years working on the mathematics of the orbital parameters
Died 1958 just before work supporting this was published

9. 1947
Frank Libby
Dated wood in glacial
material at 11,875 year before present
Technology. Established C14 dating, helped confirm timing of ice advances; 1960 Noble Prize in chemistry;
Can also apply to younger ocean cores. Independent evidence for timing of glaciation.
More evidence to support evidence of glaciers
14C => 14N + b
The half-life (t 1/2) is the name given to this value which Libby measured at 5568±30 years

10. Looking at ocean sediment
Forams about 1 mm across; used layers of fossils to construct change in temp for 100,000s of years; same pattern observed north to south in Atlantic ocean= is a global record of temps during ice age
Damn he’s cute!
Cesare Emiliani
Forams, animals made of CaCO3,
Sensitive to temp, chemistry

11. Emiliani observed changes in ocean temperature and seen worldwide.
Observation: forams fossils preserve temperature data and ocean temperature varied over time; reflect global conditions, not just local
Do global ocean and ice cores agree?

12. John Hayes 1976 23,000 oxygen isotopes <-eccentricity
<-temperature from shells
40,000
23,000
<- eccentricity
sea surface temp
Used math to test if ocean sediment record of temperature matched to orbital forcing. It did. Supports that Milankovitch was right. He compared oxygen isotopes of fossils to eccentricity.
The mechanism was recorded in sediments
<- sea surface temp
40,000

13. Ice Cores
1960s-1970s
Technology. Continuous record from ICE.

14. JOIDES Resolution 1985-present More and better ocean data, global
Put to sea in 1985, recovering sediment cores from around the world, research that is still continuing today which started in 1830’s with Aggazi
Theory – tested and testable concept which is used to explain an occurance
now we have astronimical evidence from Milankovitch
Aggazi started the evidence of glacier erratics
Challenger
More and better ocean data, global

15. EPICA – European Ice Core Project in Antarctica
Match ocean (fossils) and ice (isotope) data Are they recording the same climate?
G=glacial maximum

16. ice fossil Use whiteboard to correlate ice and ocean record.
They do match!
Ice age temp changes were global and recorded in ice cores and ocean sediment!
And we’ll see that they match orbital forcing.
ice
fossil

17. EPICA – European Ice Core Project in Antarctica

18. ?
Major
Glaciations
Understand geologic past glacial periods have occurred, not when they occurred
Flux between cold & warm periods

19. Last Glacial Maximum: Pleistocene Ice sheet
Pleistocene glacial period
Closed arctic ocean basin – promotes accumulation of ice
(Can map glacial materials)

20. Extent of ice in last ice age
No summer melting
High Albedo of snow, ice further reduced temperatures
Glaciers form/continue to form
What about sea level?

21. Glaciers leave imprint on the landscape
Groove cut underneath the Laurentide Ice Sheet during the Pleistocene, Ontario

22. Ice ages in Michigan activity

23. Activity
Using the materials provided predict & explore the ideas of objects spinning around a foci

24. Earth’s Orbital Cycles
Serbian astronomer Milutin Milankovitch
Developed model of Earth’s orbital cycles & climate change by charting the ice ages of the last 1.8 millions years ago
Orbital cycles relate to ice ages
Supported by marine sediment core data
All calculations were done by hand, which he worked on obsessively for thirty years

25. Milankovitch Cycles
Variations in the Earth's orbital eccentricity—the shape of the orbit around the sun
Changes in obliquity—changes in the tilt angle that Earth's axis makes with the plane of Earth's orbit
Precession—the change in the direction of the Earth's axis of rotation
Huge idea in science!

26. Eccentricity/Shape Long-term variation in Earth’s orbit ~100,000 years
Orbit currently almost a sphere
Cause: gravitational pull of other planets in solar system
Eccentricity animation
Currently only 3% changes between Jan & July distances from the sun (5 million km)
Amount of solar radiation received in the seasons changes, although small impact
Eccentricity Amplifies precession (wobble)
Does eccentricity explain current global warming trends?

27. Shape (Eccentricity) of Earth’s Orbit
Perihelion is the moment when the Earth is the closest to the sun in its orbit
Aphelion is the moment when the Earth is the farthest away from the sun
<- more elliptical
circle =
The data are from Berger and Loutre (1991)

28. Obliquity/ Tilt of Axis
Changes in Earth’s tilt
Medium term variation
41,000 year cycle
Affects distribution of solar radiation received at earth’s surface
23.5 degree tilt today
tilt

29. Obliquity/Tilt Why would a greater tilt support interglacial periods?
degree change in earth’s tilt
When the tilt is greater, polar regions receive more radiation (****during summer! Important to ask them what would happen in the southern hemisphere – just reinforcing the global nature of this phenomenon****), melting during summers. ****Students will say that a greater tilt reduces solar radiation reaching the poles, true in the winter, but not true in the summer.****
Changes in earth’s tilt influence the relative strength of the seasons – pronounced at the poles

30. Precession/wobble “wobble” of earth’s axis 26,000 year cycle
“wobble” of earth’s axis
26,000 year cycle
Spinning top
Earth’s axis will be pointing at Vega instead of North Star
Gradual change
Alter the dates of perihelion & aphelion & increases the seasonal contrast between seasons (****the dates of perihelion and aphelion are affected will not be affected, what is affected is the order of the seasons****)
Cause of precession is the equatorial bulge of the Earth, caused by the centrifugal force of Earth’s rotation
Does preciession explain current global climate?
animation of Precession

31. shape
tilt
High latitude winters cold enough to allow snow to accumulate
Process continues for centuries, ice sheets begin to form
Major glacial events in Quaternary coincide with phases of tilt of earth’s axis, changes in earth’s orbit & changes in earth’s rotation
wobble

33. Multiple lines of evidence:
Ice cores
Ocean sediment cores
Sedimentary rocks
Rock features
Evidence of glaciation
Orbital forcings as a mechanism for climate
Theory of Ice Ages
Astronomical Theory of Climate Change

34. Objectives
Describe the geologic evidence (hypotheses) supporting the occurrence of glaciations in Earth’s Past and how they lead to the theory of Ice Ages
Describe the variations in Earth’s orbit as described by Milankovitch and how they influence glacial/interglacial periods.

35. RQ10
How does the development of the Ice Age theory relate to the NOS ideas on the McComas paper? Cite specific people and the data they used or major technological advances.
Briefly describe how the recent geology of Michigan supports the Ice Age theory.
Explain the relationship of the eccentricity, obliquity, and precession of Earth's orbit with marine sediment data and climate change.