Earthwatcher's photos with the keyword: basalt

Originally uploaded for the Guesswehere UK group. This is the hyaloclastite front formed by the Upper Miller's Dale Lava where it originally flowed into the sea, exposed in Litton Mill Railway cutting on the Monsal Trail in the Peak District National Park, Derbyshire.

A photo of the rather faded English Nature information board explaining the formation of the hyaloclastite where the Upper Miller's Dale lava flowed into the Dinantian sea in Lower Carboniferous times.

This is a view of the Ordovician age pillow lavas on Strumble Head, Pembrokeshire. Pillow lavas are formed when molten basalt lava is erupted onto the sea floor. If the water is deep enough, the hydrostatic pressure stops the lava from exploding the sea water into steam. Instead, the liquid rock and liquid water co-exist together in an uneasy truce. The lava is extruded like toothpaste into successive oval globules, resembling pillows or sacks, hence the name. See the video clip here: oceanexplorer.noaa.gov/explorations/04fire/background/vol...

The Strumble Head lighthouse is located on Ynys Meicel ('Michael's Island') which itself is composed of the Strumble Head Volcanic Formation, mainly pillow lavas.

Another photo of the Ordovician age pillow lavas on Strumble Head, Pembrokeshire; a close-up view of one of the pillows. Radial cracking/jointing is visible, as is a hint of a finer-grained chilled margin on the edge of the pillow. Pillow lavas are formed when molten basalt lava is erupted onto the sea floor. If the water is deep enough, the hydrostatic pressure stops the lava from exploding the sea water into steam. Instead, the liquid rock and liquid water co-exist together in an uneasy truce. The lava is extruded like toothpaste into successive oval globules, resembling pillows or sacks, hence the name. See the video clip here: www.youtube.com/watch?v=y7CtJNO14YI

Another view of the Ordovician age pillow lavas on Strumble Head, Pembrokeshire. Pillow lavas are formed when molten basalt lava is erupted onto the sea floor. If the water is deep enough, the hydrostatic pressure stops the lava from exploding the sea water into steam. Instead, the liquid rock and liquid water co-exist together in an uneasy truce. The lava is extruded like toothpaste into successive oval globules, resembling pillows or sacks, hence the name. See the video clip here: www.youtube.com/watch?v=y7CtJNO14YI

A general view eastwards over the pillow lavas on Strumble Head, Pembrokeshire. Can you spot the seal?

Another photo of the Ordovician age pillow lavas on Strumble Head, Pembrokeshire. This photo shows the slaggy texture of the pillows. Unfortunately no scale as this particular exposure was not readily accessible to allow the placing of the lens cap or similar. However, the individual pillows are around 20 cm - 40 cm long. Pillow lavas are formed when molten basalt lava is erupted onto the sea floor. If the water is deep enough, the hydrostatic pressure stops the lava from exploding the sea water into steam. Instead, the liquid rock and liquid water co-exist together in an uneasy truce. The lava is extruded like toothpaste into successive oval globules, resembling pillows or sacks, hence the name. See the video clip here: www.youtube.com/watch?v=y7CtJNO14YI

Originally uploaded for the Guesswhere UK group. Calton Hill quarry was worked for basalt (roadstone or railway ballast, I think) but closed quite a number of years ago. The quarry exposed a complex section through a volcanic vent and associated dolerite sill. The columns in centre of the photo are part of the sill, but there are also an extensive series of basalt lavas, tuffs (volcanic ash) and vent agglomerates ( shattered and fragmented rock that has fallen back into the former volcano crater) some of which can be seen in the darker, finer grained material in the upper part of the cliff. The quarry was partly used as a landfill site, but that is now completed, capped and grassed over. The steep grassy slope with thin terraces in the upper left is the front limit of the landfill.

Originally posted for the Guesswhere UK group: where is Jan and what is she doing? This is the Cavedale Lava, in the upper part of Cavedale, near Castleton, Derbyshire. Jan is measuring/demonstrating the angles of the hexagonal columnar jointing in the lava flow. See where this picture was taken. [?]