INTRODUCTION

The southeast coastline of Georgian Bay between the rocky outcrops of the Canadian Shield and the Niagara Escarpment is the 'sedimentary coast'. It is a stark contrast to all other coastlines of the Georgian Bay in that it is made of soft sediment like sand, mud, and gravel rather than lithified rock. The most prominent land feature is Wasaga Beach, which is the world's longest freshwater beach. Being only a 90 minute drive from Toronto, Wasaga Beach is one of the most-visited parts of the Georgian Bay, and has been a popular vacation destination since the 1900s.

This region has been inhabited for much of the past 12,000 years when hunter-gatherers of northeast Asian decent, the Paleoindians, arrived following the retreat of the Laurentide Ice Sheet. The landscape was a largely a barren tundra or 'taiga' covered by a low-standing community of stunted bushes, mosses, lichens and mosses. But there were pockets of spruce parkland in low lying areas and animals like caribou, mammoth, and bison provided a source of meat. The people were nomadic, hunting and fishing the waters of Glacial Lake Algonquin, then migrating to quarries in the Niagara Escarpment to collect hard chert from which to make tools in the winter. Many archeological sites from this region are places where the chert (from rock formations in the Niagara Escarpment) was shaped into things like projectile points and scrapers through the process of knapping.

As the climate changed, so too did the biome, and therefore the life habits of people living in the region. With climate warming, later Early Archaic hunter-gatherers hunted a more 'modern' fauna including fish, deer, moose, and elk. Forest ecosystems became more developed, and transitioned from a spruce-parkland-type forest into a pine boreal forest. Low lake levels during the Lake Hough stage of the Holocene often meant that people could move around the 'bay' more easily following game, simply by walking rather than boating. It would have been possible at one point to walk from Manitoulin Island to the Bruce Peninsula. Unfortunately, many potential archeological sites have been flooded by subsequent rising levels of Lake Huron.

Unlike the nomadic Anishinaabe of the northern coast of Georgian Bay, the Wendat of the Huronia region (around Lake Simcoe) were settlers, building large villages and planting corn and maize in the rich soils left behind by thousands of years of lake level fluctuations, at least as early as the 14th century. This hasn't changed much: the belt between the Niagara Escarpment and Canadian Shield remains some of the best cropland in Ontario.

In this lesson, we will examine the parts of the bay surrounded by 'soft' substrate, mostly in the Wasaga Beach and Penetang Peninsula area, and how such soft substrates can be shaped fairly quickly by the effects of climate change and changes in lake level. Sedimentary coasts are at the forefront of landscape evolution because they change shape continuously with every wave that washes ashore. The study of geomorphology deals with the shape of the landscape, which we can learn how to read in order to detect environmental change of the past.

Beaches are also excellent places to learn the basics of how sediment moves through a system like a river or a beach because we can often see these processes in action in real time, on a much smaller scale.

Today, Wasaga Beach is under threat. Every year, we hear reports of storms wiping out roads or businesses. Recent high lake levels have been compounded by high levels of storm activity, while more infrastructure is being built in the region increasing the 'cost' of natural disasters. Yet, the most significant culprit is actually changes to the beach profile: over time, beaches evolve natural defences against storm activity, but those defenses are being slowly eroded by damage to vegetation and removal of natural barriers.

In this lesson, we will explore how beaches work, and how the extreme environmental change of the Holocene shaped the coastline.

By the end of this lesson, you will be able to