| P number: | P521399 |
|---|---|
| Caption: | Rock specimen of amygdaloidal trachyte. Shore, Weaklaw, Marnie Cottage, Archerfield, Dirleton, Haddingtonshire, Scotland. |
| Description: | The sample is a striking example of an amygdaloidal lava, with streaked-out whitish amygdales in a fine-grained purple-coloured groundmass. Some parts of the groundmass are a mottled greyish colour where the fine-grained iron oxides in the groundmass have been chemically reduced as a result of reactions with the amygdales. The parallel elongation of the amygdales is likely to be the result of stretching of the original gas bubbles whilst the lava was still partly molten and flowing. British Geological Survey Petrology Collection sample number EMC2476. An amygdale is a cavity, usually round in shape, found within fine-grained igneous rocks, formed from gas bubbles which have been infilled by precipitates from fluids flowing through the solidified rock. The Lower Carboniferous saw a major period of volcanic activity which produced the Garleton Hills Volcanic Rocks. This series is approximately contemporaneous with the eruption of the Arthur's Seat volcano to the west. Volcanic activity was first centred in the north of the district and then moved to the Garleton Hills where the basaltic and trachytic lavas were at their maximum thickness. The lavas were erupted under mainly subaerial conditions. |
| Date taken: | Sun Dec 01 00:00:00 GMT 2002 |
| Photographer: | McTaggart, F.I. |
| Associate: | T.S. Bain |
| Copyright statement: | NERC |
| Additional information: | EMC2476 |
| Orientation: | Landscape |
| Size: | 258.23 KB; 1000 x 770 pixels; 85 x 65 mm (print at 300 DPI); 265 x 204 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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