Blue plaque № 39532

Johannesburg, South Africa

W11 Site Volcanic Ash Deposit. These rocksbelong to the Ventersdorp Supergroup. The banded rocks that can be seen on the flat outcrop in the stream bed represent an accumulation of ash which erupted from volcanoes that existed in this vicinity 2 350 million years ago. Originally deposited horizontal

ly, they have since been tilted, and now dip at 75° to the south.

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