1. UW- Surface Process Group Alison Anders (TRMM-model precipitation) Noah Finnegan (fluvial incision, cosmogenics) Birgit Hagedorn (geochemical mass balance) Bernard Hallet (overview) Amanda Henck (landslides, erosion rates) Bretwood Higman (modeling topo., susp. seds) Dave Montgomery (overview) Matt Kuharic (cosmogenics) Dick Stewart (detrital zircons and apatite) J. Stone, A. Gillespie, B. Nelson, J. Bardeen

2. Tibet and Himalaya from East note: range is narrow

3. Central Theme: Erosion Rates Spatial patterns over a range of time scales –Time scales ranging from10 2 to 10 6 years –Current Theoretical (fluvial incision model) Mass Balance (based on diverse geochemical data)

4. Theoretical studies a.Fluvial incision rate index (scales w/ river power) show clearly that rapid erosion is currently confined to the Tsangpo Gorge, including the lower Po- Tsangpo b.Knickpoint dynamics (statics) mark active tectonic aneurysms not only at syntaxes but all along Himalaya c.Regional GIS study: relief, high low-relief surfaces, topographic trends d.Regional precipitation study (Alison, TRMM measurements) e.Simulations of drainage development with spatially varying uplift (Hig)

5. TRMM Precipitation Data 4-year compilation A. Anders

6. Mass Balance Geochemical (dissolved load + suspended load + bedload = bedrock, following Galy and France-Lanord) –i.major ions –ii. minor and trace ions Zircons (zircons from rapidly eroding area make up nearly half of zircons in upper Brahmaputra) Trace minerals (garnet)

7. Namsche Barwa Tungmai Medog Dongjiu Loulan Yarlung Tsangpo Po Tsangpo Yarlung Tsangpo 1 2 Year round sampling sites 96° 0095° 00 29° 30 30° 00 NUXIANG PARLONG 7782 m Brahamaputra Tsangpo Jiali-Parlung Siang Pasighat Sampling location Sampling locations

8. 1.Sampling in Nuxiang 2.Installation of rain gauge in Tong Mai 3.Sampling in Parlong 1 3 2

9. 10 2 to 10 4 year time scales 10 2 to 10 3 year time scale, cosmogenic radionuclides bedrock (strath) terraces provide a measure of incision rates sediments reflect basin-average exposure time (time scale: penetration depth/erosion rate, O(1m/0.001m/yr= 1000yrs) 10 3 to 10 4 yrs Catastrophic floods may be responsible for much of the erosion Chronology and frequency of floods are closely tied to chronology of glaciations

10. 10 5 to 10 6 yrs time scale from sands.Zircon fission track ages (locking in T ~ 240 to 300C) in sands from river above and below rapidly eroding areas Detrital apatite fission track ages (locking in T ~ 110C)

12. Brahmaputra (Siang), Pasighat

13. Vast Sea of Sands, NE India