1. Geography of Biomes

2. Tundra Biome
Found beyond treeline in the Arctic (Arctic Tundra) and in high mountians (alpine tundra)
Variable temperatures and rainfall
Lower elevations and latitudes: willow (Salix spp.), shrub birch (Betula nana), alder (Alnus spp.), sedges, grasses, herbs, and mosses – low arctic tundra

3. Tundra Biome
High arctic tundra (polar desert) – higher elevations and latitudes – arctic willow (Salix arctica) and heliotropic flowering plants
Perennials
Low biodiversity and biomass
With the exception of crowberry (Empetrum nigrum), arctic and southern hemisphere alpine tundra have no similar species

4. Tundra Biome Threats: Resource extraction Mining Snowmobiles
Arctic willow
Threats:
Resource extraction
Mining
Snowmobiles
Global warming
crowberry

5. Chapter 7: Changing Continents and Climates
Tuesday, February 19th

6. 19th Century Geology
Law of Superposition – 19th century geologists assumed that strata lower in the stratigraphic exposure were older than the overlying strata
Law of Uniformitarianism – assumes that processes that weathered, eroded, and deposited rock in the past were the same as those operating today
These laws used to develop geologic time scale

8. Alfred Wegener
1912 Theory of Horizontal Displacement of the Continents – similarities between Atlantic coastlines
Theory of Continental Drift ( )
Crust of continents composed of relatively light rocks. Ocean floors largely composed of dense basalts. Lighter continental rocks could float on viscous mantle of Earth and override oceanic crust

9. Alfred Wegener
Permian glacial deposits in Brazil, South Africa, India, and Australia – indicates that tropical areas once glaciated, so they must have been close to the poles at one time
Similarities in the shapes of continents, their geology, and fossils suggest closer proximity in the past
Geodetic measurements of latitude and longitude of Greenland indicated westward movement of the landmass
Continental Drift led to Plate Tectonics

10. Alfred Wegener Pangaea
Gondwanaland – Africa, South America, Australia, Antarctica, and India
Laurasia – North America, Europe, and Asia
Pangaea formed 195 mya – began to break up 180 mya with formation of Atlantic Midoceanic Ridge

11. Figure 7.3

13. Vindication – Alfred Wegener
Lystrosaurus – Triassic reptile –fossils found in Antarctica, Africa, and India – Antarctica must have been warmer in the past

14. Vindication – Alfred Wegener
Galaxioidea – freshwater fish family – found in southern South America, South Africa, Australia, and New Zealand – must have been connected in the past
WWII – sea floor mapping by submarines

15. Paleomagnetism – ancient igneous rocks are little compasses
iron or titanium point to their magnetic north
compare this to current magnetic north to determine where continents used to lie

16. Figure 7.6

17. Glaciation
Radiocarbon dating – based on measuring the amount of the radioactive isotope carbon 14 found in plant and animal remains
Greenland ice cores extend 100,000 years
Antarctic ice cores extend 400,000 years
Ice cores provide record of atmospheric chemistry
18O isotopes deposited during warmer times – 16O isotopes deposited during cooler times

18. Figure 7.7

19. Relationship between atmospheric temperature and 18O isotopes
Figure 7.9