Effigy Mounds National Monument

[iowahiker]

During March, we day hiked Effigy Mounds National Monument here in northeast Iowa and took pictures of the Mississippi ice breaking up over several days. Effigy Mounds has multiple units and all these trips went to the north unit above the visitor center. Effigy Mounds north unit has three primary Mississippi views: Fire Point above the visitor center, Twin Views in the middle, and Hanging Rock at the north end farthest from the visitor center and about 7 miles round trip depending on your route. This first series is from Fire Point view looking south. The far bluff on the right (west side) is Pikes Peak State Park which is a few miles south of Effigy Mounds. Prairie du Chien is the town on the left (east side).

Section 1, chronological view:

March 13, completely ice covered:

March 17, the Yellow River enters the Mississippi River at Effigy Mounds and is completely ice free and has help melt the edge of the Mississippi which is rising:

March 20 in the morning, ice is both melting and moving while the Mississippi continues to rise with increasing snow melt:

March 20 in the afternoon, the ice has shifted and we watched a mile long ice sheet move from above Effigy Mounds and join this ice blockage during our hike:

March 21, the ice sheets do not appear to have moved much but the ice is looking thinner and smaller:

March 26, the main channel is ice free here but barge navigation is still closed because of ice elsewhere on the Mississippi:

This picture shows how Fire Point view looks for visitors:

Barge navigation is 3 to 4 weeks behind the original schedule which was expected to start around March 10.

 

[iowahiker]

Section 2, March 20 ice sheet movement:

On our March 20 hike at Effigy Mounds NM, a mile long ice sheet moved from north of the monument, broke apart, and got stuck during our hike through the north unit which these pictures show in chronological order.

This first picture is a view north from the center view, Twin Views, at the northern view point, Hanging Rock, visible as the rock outcrop on the left which is our hiking destination. The ice at the end of the open blue water is the southern tip of the 1 mile long ice sheet which is moving south near Hanging Rock in this picture.

The ice sheet has passed Hanging Rock, our destination, where this picture is taken. The ice sheet is rubbing along the stationary ice on both sides and sounds like a strong wind blowing through conifer trees with an occasional crackling sound when a large piece of ice breaks.

This crack appeared in the front section of the ice sheet and we watched it grow:

The rear ice sheet is slowed by rubbing on stationary ice while the front sheet is carried faster by the current:

Ice fishermen enjoyed the warmer weather in the backwaters across the river from us:

The full length of the original ice sheet is captured in this picture with another break appearing in the ice sheet:

The entire ice sheet arrived back below Fire Point before we returned since the current was faster than hiking speed. The resulting ice blockage near Effigy Mounds NM remained until heavily thinned by melting. The current is pushing the ice sheets against the shore causing the blockage.

Seeing moving ice requires luck or twice weekly hiking trips since the Mississippi can clear ice in less than a week. The sounds of moving ice vary from the sound of rushing wind in some years (more small ice between sheets) to sharp loud cracking in another (large forces breaking large ice) depending on how the ice flows.

 

[iowahiker]

We are getting an early spring thaw and so took the new Panasonic camera out to Effigy Mounds NM for a day hike on February 13 and added the pictures to this thread which has March pictures from a few years ago.

The Yellow River entering the Mississippi below Fire Point with the town of Prairie du Chien across the river and the Wisconsin River entering the Mississippi in the distance with a low angle February sun in the morning. There are north/south railroads on both sides of the Mississippi and the Iowa side railroad follows the river edge along most of the route as seen here. The river level is higher than average from snow melt but not at "spring flood" depth.

Same picture but with an ice sheet floating down river.

A bluff top view looking north from the northern edge of the NM when an immature eagle accidentally flew into the picture.

Comparing identical pictures from our small sensor Canon camera (16 mpix, 1/2 inch +/- sensor) and the larger sensor Panasonic (20 mpix, 1 inch sensor, but four times the area) showed nearly the same level of detail in full sun. Both camera's default settings were easily sharpened using program settings which leaves me wondering "why not have the sharper image by default"? The larger sensor camera came in at only 1 oz heavier than the small sensor but at the cost of going down from 30x to 10x optical zoom.

 

[Casa Escarlata Robles Too]

Interesting shots of the ice movement.
Frank

 

[shellback]

Any guess on the thickness of the ice sheets from the earlier pictures?

 

[iowahiker]

Thick moving ice is typically around 6 +/- inches deep. Slabs of ice 10-20 feet long get pushed up on top of big ice sheets during collisions with no cracking or sinking. Also, the thickest moving ice can submerge the steel navigation buoys until the sheet passes over while thinner ice gets cut by the buoys. In-between ice makes a metallic banging sound as the buoy sinks and then breaks through the ice with a bang. Sometimes Bald Eagles ride the moving thick ice sheets or eat "frozen" fish in/on the sheet. We have never seen snow mobile tracks on the main channel because the current under the ice is very fast and creates thin spots. Deer and coyote tracks cross the main channel but not frequently.