A moraine can be any of several types of earth formations, gently rolling hills, high ridges, deep valleys and lakes, are some of the forms they take. A moraine is caused by a glacier’s movement across the land. Think of a glacier as a river slowly flowing down the mountain at a speed so slow it is unobservable to the human eye. Glaciers have come and gone from the earliest eras on Earth. In the Earth’s long history there have been times when it was covered by a massive ice sheet, a super glacier. The Pre-Cambrian era experienced a peri-glacial permafrost climate and the Cambrian era experienced a period of extreme glaciation referred to as “snowball earth.”
As the frozen river creeps along, it leaves claw like marks in the stone over which it flows. Because of the distinctive claw like marks geologists can easily recognize the tracks left by a glacier. Scientific theory attributes the ice ages to the Earth’s wobble which causes the climate in the latitudes south of the equator, for example, to grow colder or warmer, wetter or drier. Geologists can show where cliffs reveal that the Sahara experience a tropical climate several times in its history, containing three giant lakes that were as large as West Virginia. It seems amazing to think that there once were glaciers in Saudi Arabia and lakes in the Sahara.
The glacier picks up debris as it flows, from silt called glacial flour, sand and pebbles to boulders. It is what it does with the debris it carries along with it that forms a moraine, and the type of moraine that it is. There are nine basic types of moraines. A glacier may form several moraines, as in lateral moraines which are deposited on top of the glacier and may change as the glacier advances and melts as it retreats.
There are nine basic types of moraines: Lateral, ground, rogen, end or terminal, recessional, medial, supraglacial, washboard, and veiki.
Moraines are classified by origin or shape. Their origin can be traced back by the debris they carried down and deposited. As the Earth goes through geological changes, it does not build up layer by layer so that the depth of a dig reveals the age. Rather, the crust can push up or push under so that an ancient rock layer can end up on the top and a later layer be pushed under so that the dig unearths newer instead of later sand and rocks. This is quite valuable in determining a glacier’s origin because the moraine it creates can be linked to the age of the Earth’s layers as it migrated downward. It is easier to determine the origin of newer glaciers.
Some glaciers are known as ancient glaciers since there is little left of them to be able to ascertain their age. Medial glaciers present a problem of determining age and origin due to it being difficult to determine when they were advancing and retreating. In the case of rogen and veiki glaciers, it is difficult to ascertain their origin so they are classified by morphology (shape).
Lateral moraines run parallel to the glacier, form high ridges and some of its composition may accumulate on top of the glacier. Ground moraines form rolling hills and may be located within a lateral moraine. The terminal moraine is where the glacier last deposited its debris, but is not necessarily permanent and may become recessional as the glacier melts and reforms.
Washboard moraines were given that name because from the air they can be recognized by a low rippling series of hills resembling a washboard. The veiki moraine is combination of plateaus and ponds. The rogen moraine has a similarity to the washboard moraine, forming a ribbed landscape, the low lands often filled with water.
Our planet is formed through many processes, from mountain forming volcanoes to the lakes, ridges, and rolling hills of the moraine formed by a glacier.
Ref: Geological Magazine, Cambridge Journals Online
http://journals.cambridge.org/action/displayJournal?jid=GEO
