1. Volcanoes on the Rim 55 Million Years of Volcanism in the Pacific NW Mt. St. Helens, 1980

2. Major Events of the Cenozoic 65 55 45 35 25 15 0 5 Age (Myrs) Straight Creek Transform Fault Western Cascade Arc Challis Arc High Cascade Arc Columbia River Basalts Formation of Olympic Rocks Accretion of Olympic Rocks Major Sedimentary Basins VolcanismTectonicsOlympicsSedimentary Events Ice Ages

3. Volcanic Episodes 65 55 45 35 25 15 0 5 Age (Myrs) Western Cascade Arc (37-15 Myrs) Challis Arc (55-42 Myrs) High Cascade Arc (5-0 Myrs) Columbia River Basalts (17-6 Myrs, Most 17-14 Myrs) Yellowstone Hot Spot (14-0 Myrs)

4. Challis Arc G-2

5. Late Cretaceous/Early Tertiary Batholiths Mark the plate boundary Note the embayment

6. Plates During Challis Time

7. Formation of Challis Arc Kula Plate Farallon Plate North American Plate Challis Arc Straight Creek (Strike-Slip) Fault

8. Post Challis Arc Arc now runs north-south

9. Cascade Arc Challis Arc G-2

10. West & High Cascades G-1 West Cascade Arc (37-15 Myrs) High Cascade Arc (5-0 Myrs)

11. Why did it shift eastward? G-1 Change in dip of plate? 100 km Depth Steep Subduction Shallow Subduction Consistent with younger age of Juan de Fuca Plate

12. West Cascades in Washington G-2 Include volcanic rocks and intrusions

13. North vs. South Young Basement Rocks (Terranes) North CascadesSouth Cascades West Cascade Volcanics West Cascade Batholiths

14. North vs. South More uplift to the north Erosion

15. North vs. South Young Basement Rocks (Terranes) North CascadesSouth Cascades High Cascades West Cascade Volcanics West Cascade Batholiths

16. Some Landmarks… North CascadesSouth Cascades Mt. Rainier Tatoosh Batholith Mt. BakerSnoqualmie Batholith Chilliwack Batholith Glacier Peak

17. West Cascade Rocks in WA Fifes Peak Formation Ohanapecosh Formation Stevens Ridge Formation Basaltic andesite Andesite Rhyolite Tuff Conglomerate (lahars) Greywacke

18. West Cascade Rocks in WA Granodiorite Batholiths

19. Erosion of the West Cascade Arc Produces major sedimentary formations to the east and west G-3

20. West of the Arc Mid-Eocene D-3 Seattle Tukwila Formation

21. West of the Arc Late-Eocene & Oligocene D-4 Seattle Blakeley Formation

22. D-5 West of the Arc Miocene Seattle

23. East of the Arc John Day Fossil Beds National Monument Painted Hills (Pete Yamagata)

24. John Day National Monument, Oregon Rhino skull G-3

25. Clarno Formation (54-37 Myrs) 1."Rhinoceros" - Hyrachyus 2.Creodont - Patriofelis 3.Small browsing "horse ” - Orohippus 4.Crocodile - Pristichampsus 5.Brontothere - Telmatherium 6.Magnolia - Magnolia 7.Black walnut - Juglans 8.Palm - Sabalites 9.Horsetail - Equisetum 10.Chestnut - Castanea 11.Fig - Ficoxylon 12."Grape" - Vitis 13.Cycad - Dioon 14.Sycamore - Platanusycamore Platanus

26. John Day Formation (39-18 Myrs) 1.Sabre-toothed "tiger" - Pogonodon 2.Oreodont - Eporeodon 3.Three-toed "horse" - Miohippus 4.Tortoise - Stylemys 5.Mouse-deer - Hypertragulus 6."Dog" - Mesocyon 7.Oreodont - Promerycocherus 8."Rhinoceros" - Diceratherium 9.Chestnut oak - Quercus 10.Hawthoren - Crataegus 11.Fern - Polypodium 12.Hackberry - Celtis 13."Maple" - Acertis 14."Maple" - Acer

27. Mascall Formation (15-12 Myrs) 1.Early mastodon - Zygolophodon 2.Rhinoceros - Teleoceros 3.Giraffe-deer - Dromomeryx 4.Mountain beaver - Mylagaulus 5.Dog - Telmatherium 6.Camel - Miolabis 7.Pony-sized horse - Merychippus 8.Swamp cypress - Taxodium 9.Ginkgo - Ginkgo 10.Sassafras - Sassafras 11.Serviceberry - Amelanchier 12.Cattail - Typhaer 13.Cattail - Typha

28. Rattlesnake Formation (8-6 Myrs) 1.Short-faced bear - Indarctos 2.Single-toed horse - Pliohippus 3.Peccary - Prosthennops 4.Dog - Canis 5.Hyena-like dog - Osteoborus 6.Elephant - Tetralophodon 7.Elm - Ulmus 8.Sycamore - Platanus 9.Willow - Salix

29. Meanwhile to the East…