The Geological History Program seeks to reconstruct and understand how the landscapes of Calvert Island have evolved during relatively recent geological time (from about 35,000 years ago to present). A series of questions concerning the extent of glaciation, relative sea-level changes and landscape responses are driving this geoscience research. Many of these research questions have important implications for other programs at Hakai.
The last glacial period occurred in the late Pleistocene epoch when glacial ice covered much of the northern hemisphere including most of Canada. During that time, the Cordilleran Ice Sheet covered most of the Pacific coast of Canada. Globally, this Last Glacial Maximum (LGM) occurred between 23,000 and 19,000 years ago, although along the Pacific coast of North America the exact timing varied from about 19,000 years ago in northern British Columbia to about 17,000 years ago at the southern extent of the Cordilleran Ice Sheet near Olympia, WA. The Cordilleran Ice Sheet reached its maximum size around 16,500 years ago (Menounos et al., 2009). At the LGM, global sea level was about 120 m lower than present, although at any given location, the relative sea level (RSL) was variable, due to the interplay between glacial isostasy (loading of the Earth’s crust), eustasy (volume of water in the ocean basins) and tectonic regimes (Fig. 1). In BC’s Lower Mainland for example, RSL reached about 175 m above current levels soon after deglaciation, as the sea covered the isostatically-depressed crust. Knowledge of the post-glacial sea level history on BC’s central coast however, is lacking. Further, the exact nature and timing of glaciation along the central BC coast is poorly constrained. Our research questions are as follows:
- To what extent was Calvert Island glaciated during the Last Glacial Maximum (LGM)? Have glaciers existed on the island since then?
- How have sea levels fluctuated since the LGM in the region?
- How has the landscape evolved since the LGM? What to the landforms on Calvert Island tell us about this evolution?
- What implications do these sea-level changes and related landscape evolution have for understanding archaeological records of human history in the region?
- How have soils evolved in this landscape and what implications does this have for modern ecosystem structure and function?
To answer these questions, we are using a suite of methodologies and approaches, including traditional geological and geomorphic mapping, sedimentological and stratigraphic analyses, remote sensing (lidar and satellite data), geochronological dating (optical and radiocarbon), paleo-ecological and palynological analyses (e.g. lake coring), soil analyses, and a variety geomatics and GIS methods.
Figure 1. Examples of relative sea level curves from various parts of coastal British Columbia and Alaska (modified from Shugar et al. 2014).