PLEISTOCENE FLOODS
Glacial advances and pluvial high-stands produced catastrophic floods
SPOKANE FLOODS: most ca. 13,500 14C yr;
studied by J. Harlan Bretz (1923)
- Glacial Lake Missoula (ice dam 800 m high) 500 km3 water
- Okanogan Glacier lobe dammed Columbia River, deflected floodwaterss
- flood waters spilled accross southeastern Washington,
stripped off loess, created giant ripples
- most floods occurred after 19 14C ka
13 floods were after 13 ka, two > 6 X 106 m3/s
(Benito & O'Connor, 2004)
BONNEVILLE FLOODS: age ca. 14,500 14C yr; Malde (1968), O'Connor (1993)
- fan gravels damming outlet in Redrock pass (Idaho) elev. 5280 ft
- flood waters followed Snake River and Columbia River
SIBERIAN FLOODS (Baker et al., 1993): Altay Mts.
10,845 ± 80 14C yr
- Glacial dam 500 m
- Similar in scale to Spokane Floods, geomorphic features similar
PLEISTOCENE & HISTORIC FLOODS
PROGLACIAL LAKES (Kehew et al. 1983)
- drained into St. Lawrence Seaway
- drained into Mississippi River System
READINGS
HOMEWORK
links:
Altai Floods
Bonneville Flood
Missoula Floods (FIG.)
PBS Megaflood! (Missoula)
