Glacial Drift
Glacial drift is a general term applied to all rock material (clay, silt, sand, gravel, boulders) transported by a glacier and deposited directly by or from the ice, or by running water emanating from a glacier.
A Drift is a term of multiple uses, but in general geology it has long been a useful term applied to all kinds of material related to the Quaternary glaciation, especially till or boulder clay of ground moraines (lodgement till) and terminal moraines, etc., and meltwater products such as outwash plains (sandur), eskers, kames and other fluvioglacial products; it is not generally taken to include glacial loess or other eolian features.
The last glacial advance in Michigan is known as the Wisconsin advance. The late Wisconsin period occurred between 25,000 and 10,000 years ago. Virtually all of Michigan's present surface landforms were shaped during this time. A. Glacial Materials Glacial Drift: material transported and deposited by glacial action. Note that most glacial features are recessional, i.e., they are formed by retreating ice. Materials deposited during glacial advance are usually overridden and destroyed or buried before the glacier has reached its maximum. Till: unstratified drift (e.g., material not organized into distinct layers), ice-transported, highly variable, may consist of any range of particles from clay to boulders. Ice-deposited material is indicated by random assemblage of particle sizes, such as clay, sand and cobbles mixed together. Ice-worked material is indicated by sharp-edged or irregular shaped pebbles and cobbles, formed by the coarse grinding action of the ice. Outwash: stratified drift (e.g., material organized into distinct horizontal layers or bands), water-transported, consists mainly of sand (fine to coarse) and gravel rounded in shape. Meltwater streams flowing away from glacier as it recedes carries particles that are sorted by size on deposition dependent upon the water flow velocity – larger particles are deposited in faster moving water. Water-deposited material is indicated by stratified layers of different sized sand particles and smooth rounded pebbles, consistent in size within each band. Water-worked material is indicated by smooth, rounded particles, formed by the fine grinding action of particles moved by water. Ice-contact Material: partially-stratified or unstratified drift, usually consisting of sand and gravel. This material was originally water-deposited (stratified) on or in glacial ice, then slumped when ice melted, thus mixing the material and destroying stratification.
The posted coordinants will take you to the small park of Grove Hill. This park was the original homestead of George Grove deeded to him in 1873 by the U.S. Government. The location is the highest point in the lower peninsula of the state of Michigan. Not only is this the highest point in the Lower Peninsula it also contains some of the deepest soil deposits in North America. Near the posted coordnants you will find a wooden sign that explains the geological significants of the park.
To claim the find on this earthcache you will need to send me the answers to a few questions:
1. When standing at the posted coordinants which take you to the highest point in the park, how many feet above sea level does your GPSr read?
2. What is the estimated glacial drift deposits depth to bed rock in this area?
3. There is a small boulder at the bottom of the hill, which one of the three types of rock is it? Use explanations below to answer this question.
Sedimentary
Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Gradually, the sediment accumulates in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils.
Examples of this rock type include conglomerate and limestone.
Metamorphic
Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that occurs due to intense heat and pressure (squeezing). The rocks that result from these processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing slowly over time, on their surface.
Examples of this rock type include gneiss and marble.
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.
Examples of this rock type include basalt and obsidian.
4. What is the soil made up of at the highest point in the park.
Send me your answers via email or as a geocaching message.
Please do not post your answers in your log and do not post any pictures that will give away any answers to the questions asked to log this cache.
Thank You. 