Reading the bubbles in volcanic glass
Vesicles preserve traces of gas leaving magma, but growth, merger, flow and the cut of a specimen all change the pattern a reader sees.
A place for slower thoughts
Underfoot Atlas
Geology in stone, sediment and the ground beneath ordinary places.
Words by Ivo Calder
The archive
5 storiesFrom the notebook
The landscape beneath a limestone field
A limestone field can hide a connected drainage landscape. Dye traces, weathering experiments and sinkhole investigations show how water enters rock, travels through it and sometimes carries soil away.
How salt grows a crack in stone
Salt can leave a white bloom on stone or grow under its surface. The damaging difference lies in water, pore space and the pressure of a confined crystal.
The missing years inside a rock sequence
An unconformity marks a break in the local rock record. At Siccar Point and Grand Canyon, angles, fossils, mineral ages and fragments of older stone reveal what a missing interval can still tell us.
A river stone keeps only part of its journey
A round pebble has met other surfaces, but its smoothness is no odometer. Rock type, broken edges, intermittent floods and recycled gravel complicate the journey it seems to show.