Autoclastic basaltic breccia:
Dike rock that ground itself up while
injecting into understory of the volcano
This rock is displayed in
“Sibley's Geological
Treasures” collection on the roofed patio of the visitor
center in the Robert Sibley Volcanic Regional
Preserve. The above caption is the same that is given on-site
(June 11, 2012).
Autoclastic basaltic breccia is a rock composed of
fragments of
basalt and other rocks cemented together.
The fragments formed in place by grinding of
dike rock (tabular or sheetlike body of
igneous rock).
