Pretty River Valley Earthcache EarthCache

The topography of Southern Ontario
has been shaped in most part by glacial action at the end of the
last ice age 12000 years ago. The Pretty River Valley has some of
the best glacial features in the area. Yet with the passage of time
these features can be very hard to identify.

Glacial moraine deposits were left behind by retreating glaciers. There are many types of moraine which have been classified either by the manner in which they were formed or, if that is uncertain, by their particular topology.

The major categories are …….

• Lateral moraine : By far the most common type, lateral moraine forms ridges of debris parallel to the retreating glacier which is deposited along the margins of the retreating ice.
• Ground Moraine : Ground moraine forms an irregular lumpy topology at the base of the retreating glacier. It can be modified into drumlins by the overriding ice.
• Rogen moraine : Named after moraine at the Rogen glacier in Sweden, this type of moraine forms a series of ribs perpendicular to the retreating ice creating a tiger stripe appearance when viewed from above. It is believed that this phenomenon is caused by deposits of varying size and density being layed down in alternate fashion. Water then washed out the lighter looser material to create the effect.
• Terminal moraine : Unconsolidated debris deposited at the base of the glacier The shape of the retreating glacier can usually be inferred from the shape of this moraine as it is deposited evenly across the mouth of the glacier.
• Recessional moraine : Similar to terminal moraine but these are formed during halts in the glaciers retreat causing larger transverse ridges to form across the valley floor.
• Medial moraine : runs down the centre of the valley floor. It is formed when two glaciers meet.
• Supraglacial moraine : Debris which accumulates on top of the glacial ice and is scattered randomly as the ice retreats.

Logging Requirements.

1.  Using the altimeter on your GPSr, estimate the height of the moraine from the parking lot to the final coordinates.
2. Given the direction that the moraine runs, in which direction did the glacier retreat ?
3. What is the second glacial feature found at N 44° 25.827 W 080° 17.299? What is its average diameter ?

My thanks go to Mr John Fisher, Superintendant Pretty River Provincial Park for permission to place this cache. Thanks also to Hans Hillewaert and Luis Maria Benitez for permission to use their respective diagrams.