Tolsta Head
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Condition (NatureScot)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| F1 | Quaternary of Scotland | Favourable | — | 2005-03-31 |
Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Geological Period: Quaternary
Landscape processes: Coastal, Glacial, Periglacial
Description
Tolsta Head Tolsta Head is located on the north east coast of the Isle of Lewis. This coastal section is important for a sequence of sediments exposed at the top of the cliff. These consist of organic sands and silts overlain by a layer of till, the upper part of which has been modified by frost action and solifluction. The organic deposits formed in a small pool during an interstadial (the Tolsta Interstadial) which interrupted the middle part of the last glacial period (the Devensian) between about 38,000 and 33,000 years ago. Subsequently, after about 32,000 years ago, during the Late Devensian glaciation, the site was located near the confluence of the Scottish ice sheet and the Outer Hebrides ice cap. The glaciers deposited a layer of till on top of the organic deposits. After the ice melted, the upper part of the till was modified by periglacial processes. Tolsta Head is one of very few sites in Scotland with organic deposits of Middle Devensian interstadial age, pre-dating the last glaciation. These provide a rare insight into environmental conditions before the last glaciation, with reconstructed palaeotemperatures provisionally linked to the Greenland ice core record, and they allow the onset of the last glaciation to be dated. Tolsta Head is therefore a key reference site for reconstructing the Quaternary environmental history of Scotland and establishing the chronology of the last ice sheet glaciation.