Pictured Rocks EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(regular)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Pictured Rocks is a 1,138 acre wildlife management area named for
the limestone bluffs that line the Maquoketa River valley and home
to a unique ecosystem. During the last period of glaciers, while
much of Iowa was under a layer of ice that would one day become
vast prairie landscapes, pockets in northeast Iowa escaped. The
receding glacier's melt waters carved deep valleys in the stone and
left a few remarkable places including Pictured Rocks.
Talus Slopes
As you look at the limestone bluffs in this valley, you'll see a
distinct slope, known as a talus slope,at the base. The word talus
means 'loose rock'. The action of freezing and thawing of water as
well as erosion from water, wind, and rain has caused pieces of
rock to break off, fall, and collect at the bottom of the bluff.
The cracks, fissures, and sinkholes that allow water to get inside
the rock and freeze also allow warm summer air to enter. When the
warm air reaches the ice it cools, then makes it way out through
vents in the talus slope.
Caves & Climbing
The unique geological history of the area has also created many
caves in the rock. Archaeological evidence show this area and caves
were home to many people in the past. Today many spelunkers (cave
explorers) visit the caves and the bluffs attract rock climbers
from around the mid-west.
Indian Bluff Cave
Natural History of Indian Bluff Cave
As with many caves along the Maquoketa River, this cave was
actively formed about 70,000 years ago by the erosive action of
water running through fractures in bedrock. Scientists call this
ago of rock "Silurian" and it is made of of a dolomite (calcium
magnesium carbonate) that was originally deposited on the floor of
a vast and shallow sea that once covered Iowa. The distinctive
green algae, Cyclocrinites, is an inch or so in diameter and
resembles a golf ball. Common brachiopod shells, Crinoids (stalked
relatives of starfish), trilobites, nautiloids, and snails are also
found in these rocks.
Please answer these questions in an e-mail and follow the trail
at the posted cords (next to the plaques) and take a photo of a
Talus slope.
1) The rock that makes up Indian Bluff Cave is estimated to be how
old?
2) What were the organisms that lived on, in and above this sea
floor? (3 answers)
3) Is the area immediately next to the vents of the Talus slopes
cooler or warmer than the surrounding area?
Additional Hints
(No hints available.)