Dai

ly G

eolo

gy:

The

ride

toda

y ov

er th

e Io

wan

Su

rfac

e m

ay n

ot s

eem

all

that

ex

citin

g, b

ut s

omet

hing

qui

te

inte

rest

ing

shou

ld ju

mp

out a

t you

on

the

geol

ogic

cro

ss-s

ectio

n to

the

righ

t. Th

e be

droc

k ha

s lo

ts o

f dee

p va

lleys

cut

into

it. T

his

regi

on w

as

exte

nsiv

ely

carv

ed b

y an

cien

t riv

ers

prio

r to

cont

inen

tal g

laci

atio

n be

gini

ng a

roun

d 2.

6 m

illio

n ye

ars

ago.

The

dee

pest

bed

rock

val

ley

is m

ore

than

250

feet

dee

p! S

ome

of th

ese

valle

ys c

ut a

ll th

e w

ay

thro

ugh

the

Dev

onia

n ag

e be

droc

k an

d in

to th

e O

rdov

icia

n ag

e (~

445

mill

ion

year

s ol

d) M

aquo

keta

Fo

rmat

ion.

Dolom

ite(~4

50 m

illion

yrs. o

ld)

Till

(0.5-2

.6 mi

llion y

rs. ol

d)

Limes

tone

,Dolo

mite

& Sha

le

Shale

& Lim

eston

e

(443-4

50 m

illion

yrs. o

ld)

Ceda

rRiv

er

(385-3

95 m

illion

yrs. o

ld)

Ceda

rRiv

er

Waps

ipinic

onRiv

er

Little

Turke

yRiv

er

Turke

yRiv

er

Little

Waps

iRiv

er

As you bike across the state of Iowa you will primarily be riding on paved roads, but what are they paved with? Some are paved with concrete and some with asphalt. What is the difference? Well, both are composed mostly of aggregate, fragments of crushed limestone or dolomite and sand. It is the material that glues these fragments together that is the primary difference. Concrete (the white or light gray road surface) uses Portland cement to glue the aggregate together. Portland cement is made by firing a finely crushed mixture of limestone, sand, clay, and other materials to 2,600° F in a kiln to produce a clinker that is mixed with gypsum and crushed to a fine powder to make the cement. The cement is mixed with water and the aggregate and applied to the road base to create a concrete roadway. Asphalt is a viscous petroleum product that is heated, mixed with aggregate and applied to the road base to create an asphalt roadway. 94% of asphalt and 80% of concrete is made up from aggregate.

RAGBRAIDay 5

2017Thursday, July 27

The Science of Roads

* Cover photo: Chickasaw County Park is a former quarry. This location was designated by IGS geologists as the “type section” for the Devonian age (~385 mil-lion years old) Chickasaw Shale and Bassett members. Photo courtesy of Ryan Clark (IGS).

Protivin

Cresco

LawlerCharles City

1381 ft.

974 ft.

Elevation

Ionia

New Hampton

Little Cedar River

Cedar River

Parks and preserves

Cities and towns

USGS streamflow station

While thousands of RAGBRAI participants experience Iowa each July from the seat of their bike, hundreds of Iowans spend their July vacation from the seat of a canoe, getting their feet wet and muddy on a river cleanup event called Project AWARE. Project AWARE (A Watershed Awareness River Expedition) is the Iowa Department of Natural Resources annual volunteer weeklong river cleanup. Since 2003, more than 4,000 participants have cleaned up over 1,080 river miles across Iowa and removed 377 tons of trash, of which 76% has been recycled. Earlier this month, Project AWARE celebrated its 15th year, with more than 300 volunteers removing garbage from a 55-mile stretch of the Cedar River in north-central Iowa. Volunteers camped along the banks of the Cedar River in Charles City for two nights. As part of Project AWARE, volunteers clean up a different Iowa river each year. People come together on this annual adventure to paddle and learn about the river. Although canoes and kayaks were filled with trash each day, and rivers look better by the end of the event, the true impact of AWARE lies in the environmental education, understanding, and empowerment of the volunteers to protect, preserve, and cherish Iowa’s natural resources.

Just 12 feet downstream from the bridge crossing the Cedar River on the left bank is another USGS stream gage. All 8,000+ stream gages across the nation are a part of the USGS WaterAlert program. By subscribing to the WaterAlert service, you can receive instant, customized updates about water conditions as reported by any of the sites across the country. Whether you are watching for floods, interested in recreational activities or concerned about the quality of water in your well, you can receive updates about current conditions in rivers, lakes and groundwater when those conditions match the parameters you select. Information will be sent to you hourly or daily by text or email – you choose! Sign up at http://water.usgs.gov/wateralert.

Since 1993 the Iowa Geological Survey has conducted geologic mapping in selected areas of Iowa. In 2016, maps were made of the surficial (below) and bedrock (right) geology of the Charles City Quadrangle. Subsurface information from the drilling of water wells and other borings provide valuable information to geologists. Bedrock exposures along rivers and in quarries are also utilized to better understand what the geology is beneath our feet. Maps like these can help decision makers regulate groundwater resources, plan future urban developments, identify limestone deposits for aggregate, as well as improve understanding of watersheds and flooding hazards.

Project AWARE STATEMAP

USGS WaterAlert