An Introductory Landform Project: Moraine

The Earth surface is not a flat plane, it is constructed by various types of landforms with unique geomorphological features, including waterfall, moraine, escarpment, etc. Specifically, moraine is the substance resulted from the presence or movement of glaciers, usually consisted of soils and rock debris (Bendle, 2020).

There are several types of moraines: lateral, medial, recessional and terminal. Depending on the morphological features of landform that glaciers move pass, different forms of moraine are deposited. Lateral moraine refers to the elongation of ridges, composed by the debris from avalanche and erosion. As the glacier moves along, rocks and soils are teared off from both sides of the valley, forming the lateral moraine. As the surface of the glacier is usually horizontal, the height of lateral moraine from both sides are often the same (Evers & West). Medial moraine is formed at the intersection of two glaciers. When two glaciers merge to form a new one, the sediments are pushed to the middle. The deposits of sediments consist rocks and dirt. After the new glacier melts, the accumulated sediments form a long ridge in the middle of the valley. And as the new glacier moves, the medial moraine left behind will be parallel to the path of the movement(Britannica, 2009). Recessional moraine is the second last terminal moraine, it appears before the end point of the glacier. Forming from a standstill of the glacier retreatment, and the deposit usually appears along the valley several times. The numbers of appearance can be used to reveal past glacier movement patterns and chronological scale (Britannica, 2009). Terminal moraine locates at the furthest part of the glacier. It also contains the debris deposits of soils and rocks. After the glacier melts, the accumulated sediments form a ridge-like structure at the end, usually found near the lateral marine(Britannica, 2009).

Moraine appears at the location of present and past glaciers. This is the one and only condition of moraine formation. Figure 2. below shows the distribution of mapped tunnel valleys and moraines, which covers the Laurentide Ice Sheet. Total of 1931 tunnel valleys were recorded in the figure. Laurentide Ice sheet coverage spread across eastern, central and northern part of North America during last glaciation. Moraines were found after the glacier retreat (Prest & Fulton,1987). Part of Canada is also involved along the northern part of the giant ice sheet. There are several moraine displays in the figure, ground moraines contains clayey till shaded in blue and loamy till shaded in light green (Livingstone et al, 2013). End moraines are consisted of clayey till shaded in dark blue and loamy till shaded in dark green. Where the end moraines with clayey till locate separately in north-east area. Ground moraine with clayey till appears partially in the central part and more in the south-east part of the ice sheet. Ground moraine with loamy till almost dominates the entire Laurentide Ice Sheet, distributed evenly from west to east, north to south. End moraine with loamy till has similarly even distribution patterns, but cover less areas (Livingstone et al, 2013).

Moraine Formation Process

Moraine is a type of topographic feature formed from the deposition of glacier. Glacier pushes sediments forward and retreats backwards to create layers of marines. And its formation has close connections with glaciological and climatic conditions (Chandler et al., 2020). In general, time is a key factor to reveal the process of moraine formation. It is important to understand the influence of spatial and temporal variations' contribution to moraine formation (Chandler et al., 2020). It is easier to find the secrets behind the time scale with reliable data, such as sedimentological data, and remote sensed data from over-head perspective in a given ranges of years. Sediments are pushed in the front of ice sheet, and the height of ice sheet front can be measured. The measurements from the ice sheet front can be used to investigate the retreatments and re-advancements of glaciers (Chandler et al., 2020). Layers of moraines are formed from the movement of glacier retreat and re-advance, such as recessional moraines. As indicated before, recessional moraines are the existence of a short term standstill of glacier movement, and it ends before terminal moraines.

To have more understanding of temporal and spatial influences of moraine formation, the image below represents some detail about ice-front height changes. Figure 3 represents the height changes of ice-front at southern Fjallsjökull margin, Iceland, which was conducted in 1943. It also displays the re-advancement periods of glacier movement which is shaded in grey. (Chandler et al., 2020). This shows great examples of temporal and spatial variations contributing to the formation of moraines. The ice-sheet retreats rapidly from 1934 to 1940, only two small re-advance happens. The height of the ice-front negatively changes around 620 meters. At this certain part of moraine, the height difference is relatively higher. The rate of change in ice-front height becomes less dramatic in the following 50 years. Several re-advancements happened throughout this 5 decades gap, and the height increased by approximately 80 to 100 meters. However, the re-advancement never happened again after 1994 (Chandler et al., 2020).

On the other hand, climate condition is another significant driving force in moraine formation. Glaciers appear at locations with low temperature, so when the local temperature increases, the glaciers retreat. The rate of retreatment increases as the temperature rises, especially during the age of climate change (Marzeion et al., 2014). Melting ice sheets will carry debris from glacier margins downwards, and these sediments are commonly consisted of rocks and soils. Therefore, temperature changes are have important influence on moraine formation (Harrison et al.,2018). The moving glacier will carry more than just sediment rocks and soils, it also carries a great amount of water storage. As a result, moraines do not only appear at places with valleys and ridges, it also appears at glacial lakes (Harrison et al.,2018). The deceasing trend from Figure 3 also illustrates that the retreatments start from around 1994, and continues sustainably until the last recorded measurement in 2014 (Chandler et al., 2020).

Overall, moraine formation is influenced by temporal, spatial and temperature factors. Each of these factors can have determining influence on location, types, and sizes of the moraines.

A Case Study: Oak Ridges Moraine

Rather than looking at moraine formation in general, a real world example, Oak Ridges Moraine, will help explain how moraine forms. What are the characteristics of the temperature, spatial, temporal factors affecting Oak Ridges Moraine? Oak Ridges Moraine, a prominent moraine landform located in southern Ontario, is one of the linear moraines in Great Lake area (Barnett et al., 1998). It is constructed by porous debris from glacier movement, with around 180km in length and up to 25km in width (Wood, 1999).

By looking at its geological setting and backgrounds, "the ORM comes across around 160 kilometers, extends from Niagara Escarpment to beyond Rice Lake, and consists high sandy ground in a drainage" (Barnett et al., 1998). A fundamental factor that forms western margin of ORM, is the bedrock formed from Niagara Escarpment. It has potential availability to control water levels through the channel system created along escarpment during moraine formation(Barnett et al., 1998). Southern margin of ORM comes from marginal zones of Laurentide Ice Sheet(Shaw et al., 1996). The north part of the ORM, "Peterborough drumlin field forms a east-southwest-oriented surface, and deposits connects with Newmarket Till"(Barnett et al., 1998). ORM consists large amounts of areas with hummocky topography, uplifted plains and ridges small in size. "Four distinct features are: large, elevated, wedge-shaped bodies"(Barnett et al., 1998).

The developments of ORM divides into four stages: stage one-subglacial sedimentation, stage 2-Subaueous fan sedimentation, stage 3-fan to delta sedimentation, and stage 4-Ice-marginal sedimentation(Barnett et al., 1998). Initially, moving channels are created by melting water, such as the Rice Lake with a east to west directional channel(Barnett et al., 1998). To continue, subglacial cavity created by initial fragmentary expands in the second stage. Sedimentation process dominates by gravels, and extended sedimentary continues around 1 to 2 kilometers downhill (Barnett et al., 1998). Furthermore, ice-confinement happens in stage 3, abundant fine sand and silt rhythmites were deposited. Rhythmites display as thickest part in the basins, with under water depth of 100-200 meters. Fan to deltaic sedimentation happens where water goes into gaps at Campbelliville on Niagara Escarpment(Barnett et al., 1998). In the last stage, upper part of moraine sediments are interbedded glaciolacustrine and bedded diamictons. The sedimentation happens partially deposit ice marginally in Humber River basin(Barnett et al., 1998). It is difficult to determine the significance and contributions among these four stages. Because there are sediments not extracted and still berried underground. Deeper deposits needs to extract to find that whether the ORM formed in time sequence or more synchronous sedimentation(Barnett et al., 1998). Oak Ridges Moraine is formed under complex process, and not completely find out which part of the four wedges contribute the most.

Conclusion

Moraine is generated by the combination of glacier retreats and re-advancements. The deposits carried along by the glacier form different moraines with various sizes and shapes. Currently, one of the important factors affecting the formation of moraines is temperature. Under climate change, the rising temperature speeds up the glacier retreatments. This means the glaciers will carry more sediments and greater amount of water storage. The water also deposits downhill and form lakes. Lakes are beneficial because they can potentially become additional drinkable water reservoirs. The Oak Ridges Moraine from the case study has great amount of water storage and becomes reliable water resource. It brings a lot of benefits to the community, but human activities can potentially reduce the quality of reliable resources from ORM, such as water resources. The balance between urban development and environmental sustainability needs to be considered. On the other hand, floods may cause flood disasters and negatively influence the society. Therefore, moraines have the potential to positively or negatively contribute to the society, depending on climate changes as well as urbanizations.

References

Barnett, P. J., Sharpe, D. R., Russell, H. A. J., Brennand, T. A., & al, e. (1998). On the orgin of the Oak Ridges Moraine. Canadian Journal of Earth Sciences, 35(10), 1152-1167. http://myaccess.library.utoronto.ca/login?qurl=https%3A%2F%2Fwww.proquest.com%2Fscholarly-journals%2Fon-orgin-oak-ridges-moraine%2Fdocview%2F218914475%2Fse-2%3Faccountid%3D14771

Bendle, J. (2020, June 22). Moraine types. AntarcticGlaciers.org. Retrieved March 28, 2022, from https://www.antarcticglaciers.org/glacial-geology/glacial-landforms/glacial-depositional-landforms/moraine-types/

Britannica, T. Editors of Encyclopaedia (2009, August 7). moraine. Encyclopedia Britannica. https://www.britannica.com/science/moraine

Chandler, B. M. P., Chandler, S. J. P., Evans, D. J. A., Ewertowski, M. W., Lovell, H., Roberts, D. H., Schaefer, M., and Tomczyk, A. M. (2020) Sub-annual moraine formation at an active temperate Icelandic glacier. Earth Surf. Process. Landforms, 45: 1622– 1643.  https://doi-org.myaccess.library.utoronto.ca/10.1002/esp.4835 .

Harrison, S., Kargel, J. S., Huggel, C., Reynolds, J., Shugar, D. H., Betts, R. A., Emmer, A., Glasser, N., Haritashya, U. K., Klimeš, J., Reinhardt, L., Schaub, Y., Wiltshire, A., Regmi, D., & Vilímek, V. (2018, April 9). Climate change and the global pattern of moraine-dammed glacial lake outburst floods. The Cryosphere. Retrieved March 28, 2022, from https://tc.copernicus.org/articles/12/1195/2018/

Livingstone, Stephen & Clark, Chris. (2016). Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation. Earth Surface Dynamics. 4. 567-589. 10.5194/esurf-4-567-2016.

National Snow and Ice Data Center. Glacier Landforms: Moraines | National Snow and Ice Data Center. (n.d.). Retrieved March 28, 2022, from https://nsidc.org/cryosphere/glaciers/gallery/moraines.html

Wood, J. D. (1999). Oak Ridges Moraine. Canadian Geographer, 43(2), 208-209. http://myaccess.library.utoronto.ca/login?qurl=https%3A%2F%2Fwww.proquest.com%2Fscholarly-journals%2Foak-ridges-moraine%2Fdocview%2F228338057%2Fse-2%3Faccountid%3D14771 Wood reviews "Oak Ridges Moraine" compiled by the STORM Coalition.