Lava Soil Profile, Floreana Island, Galapagos Islands

September 06, 2017


Photographer: Raymond Murphy
Summary Author
: Raymond Murphy

The photo above shows soil layering that can occur in an active volcanic environment, in this case on Floreana Island in the Galapagos archipelago of Ecuador. It was taken in an eroded embankment at Punta Cormorant, on the northern coast of Floreana Island. The island itself is a low shield volcano (Floreana volcano) that's been active for at least 1.5 million years. Approximately 50 scoria (cinder) cones are distributed around the island. One of these cones is located at Punta Cormorant. The terrain here it is largely covered by gravel-like, pea-sized (or smaller) volcanic cinders.

As the first picture illustrates, the top few inches of the soil (the darkish part) are relatively free of fine organic matter, but below that (the ochre-colored part), the interstitial spaces have filled in and provide an environment for plant roots. This cross-section also shows the layering resulting from many cinder deposition events over the years.

Note that the white-barked tree (top photo) is a palo santo (Bursera graveolens), a species that covers the arid hillsides on Floreana; the low green shrubs (top photo with close-up on bottom photo) are Maytenus Octogona, an arid-adapted plant with thick, stiff leaves that are oriented vertically to minimize evapotranspiration in the intense equatorial sunlight. Photos taken on May 27, 1979.