Keg
Cree
k
Till
(0.5
-2.6
mill
ion
yrs.
old)
Loes
s (1
2,00
0-30
,000
yrs
. old
)
Sand
ston
e(9
0-10
0 m
illio
n yr
s. ol
d)Li
mes
tone
& S
hale
(305
mill
ion
yrs.
old)
Shal
e(3
00 m
illio
n yr
s. ol
d)
Silv
erCr
eek
Wes
tN
ishn
abot
naRi
ver
Wal
nut
Cree
k
East
Nis
hnab
otna
Rive
r
TRFZ
Dai
ly G
eolo
gy:
Toda
y’s
ride
bri
efly
cros
ses
the
Loes
s H
ills
land
form
regi
on
nort
h of
Tab
or. L
oess
, or w
ind-
blow
n si
lt, o
rigi
nate
d fr
om th
e an
cien
t Mis
sour
i Riv
er d
urin
g th
e la
st “
Ice
Age
” fr
om 2
4,00
0 to
12
,500
yea
rs a
go. P
enns
ylva
nian
-ag
e be
droc
k co
nsis
ting
mos
tly
of sh
ale
and
limes
tone
und
erlie
s to
day’
s ro
ute,
with
poc
kets
of
Cre
tace
ous-
age
sand
ston
e in
th
e G
lenw
ood-
Mal
vern
are
a.
The
Thur
man
-Red
field
Fau
lt Zo
ne (T
RFZ
), w
ith o
ver 3
00 fe
et
of o
ffse
t obs
erve
d, s
outh
east
of
Tab
or m
arks
the
east
ern
boun
dary
of t
he b
illio
n-ye
ar-o
ld
Mid
Con
tinen
t Rift
Sys
tem
.
For the 11th year the Iowa Geological Survey (IGS), the U.S. Geological Survey (USGS), and the Iowa Department of Natural Resources (IDNR) return as “Human and Natural Resource Partners”. Learn about the Land provides daily brochures describing interesting landscape, geologic, and other natural resource features and factoids along the RAGBRAI trail. Look for USGS volunteers as they distribute the Learn about the Land brochures in RAGBRAI campgrounds.New this year is a partnership with the University of Iowa’s Mobile Museum. This 40’ RV will be at Expo and along the entire route distributing Learn about the Land brochures. Stop by to pick up your brochures and see the all new educational displays inside!Special thanks to the Iowa Limestone Producers Association (ILPA) for assisting in the production of the Learn about the Land daily brochures. With their help, we are able to provide interesting information about one of Iowa’s greatest natural resources…limestone!
www.iowageologicalsurvey.orgwww.ia.water.usgs.govwww.limestone.org
* Cover photo: The loess hills approaching dusk.
RAGBRAIDay 1
2016Sunday, July 24
Learn about the land Partners
!(
We
st
Ni s
hn
ab
otn
a R
ive
r
We
st
Ni s
hn
ab
otn
a R
ive
r
1270 ft.
928 ft.
Elevation
Glenwood
Malvern
Tabor
Randolph
Shenandoah
Imogene
Gravel Loop
USGS streamflow
Parks and preserves
Cities and towns
For a very short stretch on Day 1, riders will cross the Loess Hills landform region. (Loess rhymes with bus). The City of Glenwood is located atop the loess hills, and US HWY 275 north of Tabor is positioned at the boundary of the Loess Hills and Southern Iowa Drift Plain. Iowa’s steeply rolling Loess Hills are composed of very thick accumulations of silt deposited during glacial periods. Loess, or wind-blown silt, originated from the historic Missouri River and accumulated on the landscape during the last “Ice Age” from 24,000 to 12,500 years ago. During warmer periods the ancient Missouri River would carry and deposit fine sediment from the northern glaciers along its banks. During cold periods, strong westerly winds would blow loess out of the valley onto the adjacent landscape. Near Glenwood, the loess thickness may reach 50 feet.
Buried hundreds of feet beneath the surface in western Iowa lie ancient river channels carved into bedrock. South of Glenwood lies one of these bedrock valleys. Called the Glenwood Chute, this river is related to the ancestrial Missouri River Valley and corresponds to the Platte River Valley in Nebraska. Over 100 feet of sand and gravel can be found in the bottom of this bedrock valley. The Glenwood Chute connects to the larger Fremont Channel, which was formed by large volumes of water from melting glaciers 2.6 million years ago. Both of these channels are buried by as much as 650 feet of glacial till and loess. The sand and gravel in these channels are an important source of water for many Iowa citizens. Sometimes these are flowing wells!
Water Quality MonitertingMany things affect water quality. They are complex and interconnected, and occur at timeframes of min-utes (e.g., flash floods) to decades (e.g., evolving management practices). Landscape use also contributes
to the quality of our waters. In recent years, a major water-quality concern has been how much nitrate & phosphorus is transported (load) downstream. These nutrients are natural and a necessary part of every healthy ecosystem, but an imbal-ance in our rivers, streams, lakes, and es-tuaries can lead to serious environmental issues. As you cross the West Nishnabot-na River, you will pass by a USGS streamflow station that is equipped with wa-ter-quality sensors. Real-time data for the nation-wide USGS network are available online at: http://waterwatch.usgs.gov/wqwatch
Back by popular demand! The gravel loop this year takes riders to Imogene. It requires about 1,000 tons of gravel per mile of road with another 150 to 400 tons per mile in annual maintenance. That means the approximately 17.25 mile rural route took more than 17,250 tons of gravel to make, that’s enough gravel to fill over 1,000 standard dump trucks!
The Loess HillsBuried channels