Langdale Pikes
Also within
Condition (Natural England)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| NY277079 | — | Favourable | 8.87 | 2020-10-05 |
| NY278062 | — | Favourable | 6.05 | 2020-09-23 |
| NY279067 | — | Favourable | 115.72 | 2020-09-23 |
| NY279078 | — | Favourable | 83.89 | 2020-09-23 |
| NY285073 | — | Favourable | 98.01 | 2020-09-23 |
| NY287076 | — | Favourable | 8.54 | 2020-09-23 |
| NY294074 | — | Favourable | 147.13 | 2020-09-23 |
| NY295068 | — | Favourable | 4.97 | 2020-09-23 |
Geology & landscape
Geological Feature: Geological Fault · Geological Period: Ordovician · Rock Type: Breccia
Landscape processes: Volcanic / Igneous
Description
Description The Langdale Fells exhibit continuous natural sections through part of the Ordovician Borrowdale Volcanic Group, illustrating the formation of a major volcanic centre which collapsed to form acaldera lake. The stratigraphically lower parts of the site provide sections through much of the Scafell Caldera extrusive volcanics. The Airy’s Bridge Formation here includes the thickest development of the Bad Step Tuff, a highly welded rhyolitic tuff, in part flow banded and auto brecciated towards its top. Continuous sections of the massive intra caldera Crinkle Tuffs ignimbrites display rheomorphic folds with thin mesobreccia lenses. Stratigraphically above these, the site exposes the entire Seathwaite Fells Formation, a superb caldera lake sediment sequence of volcanically derived sandstones, siltstones, conglomerates, breccias and tuffs, mostly of andesitic to rhyolitic composition. The area includes the type locality for the Harrison Stickle Member. In addition, the Pavey Ark Member exhibits the only subaqueous spatter bearing lag breccia deposit recorded in the world and is comparable with recent on land caldera deposits such as at Santorini. The Grave Gill and Dungeon Gill volcano tectonic faults represent exhumed caldera floor faults with a complex reactivation history. The entire succession is repeated by the east–west trending Langdale reverse thrust, a reactivated volcano tectonic fault. Differences in the sedimentary sequence on either side of the fault indicate that this was an active unstable scarp in the caldera floor. Other indications of caldera floor activity are intracaldera mesobreccias with separate blocks up to two metres across, formed by rock avalanches during caldera collapse.