1. Continental Drift Plate tectonics

2. (video in the library notes on video in binder) A. HISTORY AND THEORY Proposed by geologist Alfred Wegener 1912 initially incorrect explanation but the modified theory is widely accepted (seafloor stationary and the continents move WRONG)

3. see text diagram (pgs. 11-12) 10 major plates and many minor plates up to 100 km thick Continents ride (less dense material) on the moving crustal plates These are the possible events at the boundary between the plates

5. Seafloor Features: Deep Ocean Plate Boundaries –Ridges (Rises), Trenches, Transform Faults, Fracture Zones

6. These are the possible events at the boundary between the plates 1.slide 2. spread 3 subduction

7. These are the possible events at the boundary between the plates 4 subduction w/ continents 4a later subduction w/ continents

9. B. EVIDENCE OF DRIFT 1. OLDa. puzzle pieces b. fossil distribution c. sedimentary layers "Gandwanan Sequence" similar geology on 4 southern hemisphere continents sand stone with coals black shale glacial till

11. 2. NEW evidence (POST WW II) a. earthquake shallow quakes at ridges and boundaries shallow and deep quakes at trenches distribution "Ring of Fire“ b. movement can be measured from space

12. c. magnetics- paleomagnetism magnetic reversals of earth's magnetic field show a chronology draw an example of the Mid Atlantic Ridge

13. C. BIOLOGICAL CONSEQUENCES of continental drift 1.Vent Communities Fissures at plate boundaries, super heated water spews minerals, gases onto the ocean floor. May exist for several hundred years (NO LIGHT) Energy rich chemical begin the food chain. ? How do animals in the community find the next vent that may be hundreds of miles away?

16. VI. SEA LEVEL CHANGES fig. 1-11 A. EVIDENCE The EVIDENCE terrestrial sediments have been observed in marine environments Evidence of sea level drop 15,000 years ago down 120m (400 ft) Extends land to the continental shelf

18. B. IMPACT ON THE BAHAMAS Paleoprovidence (handout) Bahamas "baja mar" shallow sea 700 islands, cays, and rocks 5,380 sq. miles 50 miles from US mainland

20. 1. sea level changes the growth pattern of coral islands are made of limestone deposited by coral arragonite) The sea may have been higher or the land uplifted

22. 2. Biologically this is significant. decreases migration and dispersal distances between land masses. Unites separate islands. 3. Tongue of the Ocean 10,000 ft. valley