The Summerland cannonballs are a unique geological feature found in and around the community. (Contributed)

The Summerland cannonballs are a unique geological feature found in and around the community. (Contributed)

Cannonball rock formations unique to Summerland

Geologists are studying the round rocks found in the community

Summerland’s landscape was shaped by glaciation and all the mountains surrounding the community — Giant’s Head Mountain, Conkle Mountain, Crater Mountain Rattlesnake Mountain and Cartwright Mountain — are extinct volcanoes.

One of the most unique geological features in the community are the Summerland cannonballs.

These spherical shaped cannonballs vary in size from ping-pong ball size to massive two-metre wide stone. Often the cannonballs have a slight tear drop shape.

READ ALSO: Active volcanoes in South Okanagan

READ ALSO: Rock layer can be seen along the highway at Sumac Ridge cut

The surfaces of cannonballs have been described as ‘crusty’ and the interior has minimal crystallization.

During the 1940s and 1950s, these cannonballs were sold at our fruit stands, but today have become rare to acquire.

These rocks are found only in the volcanic Marron formation. Cannonballs are not concretions, characteristically found in sedimentary rock.

Previously, it was thought that these cannonballs were lava bombs that were expelled from volcanoes into the air and promptly falling into a surrounding lake and quickly cooled. This theory has been disputed.

Since September 2020, two geologists are studying the formation of Summerland cannonballs.

The density of the rock is similar to the density of basalt. The surrounding matrix of rock is slightly less dense. These scientists now believe that the cannonballs were not formed by airborne lava.

To maintain its round shape they believe dripping, inside slurry of volcanic ash, formed cannonballs. This is similar to the formation of lava pillows.

The highest concentration of cannonballs appears to be found just north of Bentley Road and the speculated source of the lava was from the extinct volcano; Rattlesnake Mountain.

The geologists wish to determine the distribution of cannonballs in Summerland. Could these cannonballs originate from other, now extinct, volcanoes.

Anyone who knows of other locations where cannonballs have been found is asked to contact David Gregory at 250-494-9030.

Unique cannonball rock formations can be found around Summerland. (Contributed)

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