Download Geology/hydrology of the Chehalis River

Lava, fossils, glaciers, faults,
and floods—The mysterious
geologic history of the
Chehalis River
Pat Pringle
Centralia College
2,750 sq mi
Chi-ke-lis (“shifting sands) Hitchman, 1985
“Most of the precipitation falls between October
and May. The driest months are July and August.”
http://www.crcwater.org/newsltr/news9810.html#75
• “The Chehalis River isn’t quite sure where
it’s going; it rises in the southern Willapa
Hills, flows north to near Rainbow Falls, then
east to Chehalis, then northwest between
the Willapa Hills and the Black Hills, and
finally west to Grays Harbor and the Pacific
Ocean”
•
USGS Chehalis Basin
map link
Scott Babcock & Bob Carson: Hiking Washington’s
Geology, 2000
Chehalis Basin
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Chehalis River
Ongoing revolutions
Length 115 mi (185 km) [1]
Watershed 2,660 mi² (6,889 km²) [2]
Discharge at near Satsop, WA
- average 6,425 ft³/s (182 m³/s) [3]
- maximum 64,000 ft³/s (1,331 m³/s)
- minimum 440 ft³/s (12 m³/s)
Discharge elsewhere
- mouth (Grays Harbor) 11,208 ft³/s (317
m³/s) [2]
• Plate tectonics…
tectonics…
• Earth systems science…
oceanscience… including oceanatmosphere processes…
processes…
• Earth/environmental history
1
Water Cycle – continuously collected,
purified, recycled and distributed
Here we are on the leading edge….
Flowing
artesian well
Precipitation
Well requiring a pump
Evaporation and transpiration
Evaporation
Confined
Recharge Area
Runoff
Aquifer
Stream
Infiltration Water table
Infiltration
Lake
Unconfined aquifer
Less permeable material
such as clay
Confined aquifer
Confirming permeable rock layer
• This is where the Juan de Fuca oceanic plate dives beneath North
America and sinks into the earth’s deep mantle.
• This zone of plate convergence is called the Cascadia subduction
zone, and it is the source of our rocks, geologic hazards, and
landscape.
Cascadia is part of a global system
1
Seattle
Subduction
also creates
earthquakes
Portland
Earthquakes:
Green = N. Am plate
Red = J. de Fuca plate
plat
Triangles=major volcanoes
2
Cascadia megathrust,
source of great
subduction zone
earthquakes (blue area)
• Plate motion is created by earth’s internal
heat.
• Hot mantle rises, partly melts to form new
crust at spreading ridges (1), then cools
and sinks at subduction zones (2).
Note clustering of
upper plate (green)
earthquakes in
Washington
A bigger picture is
revealing..
North America
plate
Pacific plate
Small Cascadia plates are caught between two larger
plates (relative motion shown by red arrows).
2
Tape
here
Tape
here
Page 4
Tape
here
Wrangellia
Subduction
zone
backsteps
Seattle
Spokane
Quesnellia Terrane
Part of the
Intermontane
Superterrane
Portland
Tape
here
Insular
Superterrane
Seattle
Spokane
Farallon
Plate
Cut
along
dotted
line
5. Docking of Okanogan
Highlands
(~170-180 m.y.)
Portland
6. Docking of the North Cascades
100 – 60 Ma
8. Docking of Olympic
Peninsula
(50 to 30 m.y.)
Page 6
Seattle
Page 5
Spokane
Seattle
Olympic Subduction
Zone
Siletzia
Terrane
Portland
7. Eocene to Miocene Sandstones and Volcanics
(55 to 20 m.y.)
Spokane
Portland
Tape
here
Cut
alon
g
dotte
d
line
9. Eruption of the
Columbia River Basalts
17-6 Ma
Seattle
Between ~17 and 6 Ma flood basalts of the
extensive Columbia River Basalt Group erupted
from fissures near the WA-Idaho-Oregon border
areas and inundated the Columbia Basin and all
the way to the Pacific.
Spokane
Portland
3
Some of the Grande Ronde flows
reached what is now the upper
Chehalis River—perhaps a few
weeks after they were erupted!
They form Rainbow Falls.
Big blocks are rotating—north-seeking
magnetic directions captured when Coast
Range lavas cooled now point eastward.
We are also undergoing
contraction as we get
compressed S to N
v
N
v
Columbia River
basalt exposed at
Wahclella Falls in
the Columbia
River Gorge.
Coast Range basalt - similar to Hawaiian Islands 52 millionmillion-yearyear-old submarine
was accreted
to
the continent about 50 million
Trask River
yearspillow
ago; basalt,
then rotated
clockwise.
W. Oregon has been
rotating clockwise for
millions of years.
• Rotation rate of 1.2° per Million
years for at least 50 million
years, based on
paleomagnetic study.
• Rotations are less to N, S, and
E..
(pie-shaped wedges are uncertainties
about mean rotation from
expected north seeking direction;
modified from Gromme et al.,
1986)
GPS velocities 1995-2005
Velocities rotate
clockwise (block
rotation)
• decrease away from
coast (compression
above SZ)
– Blue are
campaign sites,
red are
continuous sites
(PBO)
– Many institutions:
RPI, UW, GSC,
USGS, OSU,
NGS, PANGA,
PBO
•
McCaffrey, Qamar, King,
Wells, et al, s GJI, 2007
Northwest Block
model for long-term
motion
• Sierra Nevada dragged
northward by Pacific
Plate
• Oregon (pink) pivots
clockwise to get out of
the way
• Washington (green)
gets squeezed against
Canada- hence all the
earthquakes and faults.
• SE Oregon and
Nevada Stretch to fill in
the gap behind rotating
block
Geologic map-Chehalis basin area
Note not only the patchwork of geology but also the
structures that control the river’s shape and geography.
4
Geologic-south Chehalis basin
Geologic-north Chehalis basin
Geology-Olympics-Black Hills
A look at the stratigraphy of the region
Lithologic Indicators of Climate
5
http://www.scotese.com/
legend.htm
4
3
Major
“Ice Ages”
in Earth
History
Tillite of
Windermere: Toby
Formation
2
1
http://www.scotese.
com/climate.htm
5
Climate Since the Cenozoic (65 Ma to today)
Northcraft Fm
Ma = mega annum (1 my)
“Global conveyor belt”
Vashon Fm
Blakeley Fm
Ohanapecosh Fm
Photo donated by Larry McMIllan
plate tectonics
Late Cretaceous, 80 Ma
Miocene, 20 Ma
http://www.ci.tenino.wa.us/TeninoQuarry1_small.jpg
Ron Blakey
Stefan Rahmsdorf
modern
Northcraft Formation volcanic rocks
Eocene McIntosh Formation:
Tenino Sandstone
Pe Ell volcanic rocks near Rock Creek
6
Eocene nearshore
marine fossils—like
Willapa Bay! Why in
Centralia?
<= Portunites triangulum Crab,
Eocene, Wahiakum Co., Washington
http://www.geo-tools.com/fossils.htm
A tonstein in the Chehalis
Coal Mine. A kaolinitic
remnant of an ancient
tephra deposit!
http://orerockon.com/For_sale.htm
8. Docking of Olympic
Peninsula
(25 to 30 m.y. or earlier??)
Seattle
Spokane
Olympic Subduction
Zone
Siletzia
Terrane
Portland
Tape
here
Cut
alon
g
dotte
d
line
7
Columbia River Basalts along SR
6. What is now the upper Chehalis
River received basalt flows from
the ancestral Columbia River!
recent events: Ice Age Earth
• repeated cycles of gradual
cooling and rapid warming
• global glaciation and
deglaciation
• cyclic changes in Earth’s
orbit around the Sun
A buried forest along the
Neawaukum River south of
Chehalis.
• feedbacks within Earth’s
climate system
From Ruddiman, Earth’s Climate
Today’s Puget
Lowland
Puget Sound
From 1.8 Ma to 11,500 ka – Pleistocene glaciation!
Puget Lobe of the
Vashon Glacier
Ice
~16,000 yr ago
(map  D Molenaar, 1987)
8
Puget Sound During the Ice Age (A Modern
Analogy - Columbia Glacier, AK)
Austin Post
Tacoma
Olympia
?
Elma
?
?
?
?
Tenino
?
Centralia
Andesite boulders, Tenino at SR 507.
9
Earth’s orbit & climate
• gravitational
interactions among
planets & sun
• cyclic changes in
Earth’s orbit
UCAR graphic
• cycles in the amount
of solar energy
arriving at Earth’s
surface
• intensity of seasons
Morrison (1991) marine oxygen isotope stages
Glaciations (cool)
Interglacial times (warm)
Stage numbers = even-numbered peaks (at top) are glacial
maxima, and odd-numbered troughs (at bottom) are
interglacial minima. Red areas = interglacial episodes.
• Chehalis River—Thanksgiving flooding
1990—from I-5. View to South.
Gases bubbling out of
the Chehalis River near
Elma a few months after
the Nisqually earthquake
of 2001
10
N. Hemisphere changes in avr temperature for 1000 to
2000 (from tree rings and glacial ice). Note distinct
increase in temperature since 1900.
FIGURE 10-21. Wind and ocean temperature conditions are
shown during (a) normal conditions with strong trade winds and
(b) El Niño conditions with weak trade winds. El Niño leads to
warm temperatures off the west coast of South America.
Fig. 10-21, p.260
(b) During normal, or the opposite extreme, La Niña conditions,
southwestern BC and WA are wet, as are areas immediately
south of the Great Lakes. Western Canada,
Fig. 10-22b, p.260
Fig. 8-2, p.203
(a) El Niño promotes greater winter precipitation in some areas,
less in others. During El Niño, SW US is wet, in contrast to its
normally dry weather, while the SE states are cooler than normal.
Fig. 10-22a, p.260
Western and eastern Canada are warmer.
FIGURE 10-24. Sea-surface temperature anomalies in the midPacific Ocean are shown from 1900 to 1950 and 1950 to 2003. El
Niño shows abnormally high sea-surface temperatures.
Fig. 10-24, p.262
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Most of the observed warming in the past 50
years is attributable to human activities
FIGURE 7.30 Typical winter sea surface temperature departure from
normal in °C during the Pacific Decadal Oscillation’s warm phase (a)
and cool phase (b). (Source: JISAO, University of Washington, obtained
via the http://www.jisao.washington.edu/pdo/ Used with permission of
N. Mantua.)
Fig. 7-30, p.196
Land areas are projected to warm more than the
oceans with the greatest warming at high latitudes
Annual mean temperature change, 2071 to 2100
relative to 1990: Global Average in 2085 = 3.1oC
21st Century Global Warming
Average temperature could increase beyond the year-to-year variability
observed in the PNW during the 20th century as early as the 2020s
Projected range of globalscale warming by 2100:
2.5-10.5°F (1.4-5.8°C)
Warming expected through
21st century even if CO2
emissions end today due to
persistence of greenhouse
gases.
Estimated
atmospheric
lifetime of major
greenhouse gas
(per molecule)
Figure source: IPCC 2001
Carbon Dioxide ~60% of warming
5 to 200 years
Methane
~20% of warming
8 to 12 years
Nitrous Oxide
~6% of warming
~120 years
CF4 (Perfluoromethane)
>50,000 years
Data source: IPCC 2001
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Main Impact (I): Less Snow
Warmer temperatures contribute to more winter
precipitation falling as rain rather than snow, particularly in
transient (mid-elevation) basins
Changes in Simulated April 1 Snowpack for the Cascade Range in WA and OR
Current Climate
~ 2040s (+3°F)
~ 2060s (+4.5°F)
-44%
Main Impact (II): Altered Streamflows
• More winter rain → higher winter streamflows
• Warmer temperatures → earlier snowmelt and a shift in
the timing of peak runoff
• Lower winter snowpack → lower spring and summer
flows
Projected streamflow changes in the Quinalt and Yakima Rivers
-58%
+3.6 to +5.4°F
(+2 to +3°C)
In (mm)
(note: under new scenarios, light blue bands are more likely to be seen mid-century (2050s) rather than 2040s
Requested Resources
The following are provided as a result of questions at the Northwest
Sustainability Conference:
• More information on the new (2005) climate change scenarios:
http://www.cses.washington.edu/cig/fpt/ccscenarios.shtml
• A nice synopsis of the science is available in the Environmental Law
Institute’s “Reporting on Climate Change: Understanding the Science, 3rd
edition” (2003). http://www.elistore.org/books_detail.asp?ID=10924
• For periodic updates on CIG research, meetings, or other information,
consider joining the CIG’s “Climate Update” list serve. The most recent on-line
CIG newsletter and information on how to sign up for the list serve are available
at http://www.cses.washington.edu/cig/outreach/newsletter.shtml
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