Fault History


Discovery of the fault

In the 1800’s, as copper mining developed in the Keweenaw, geologists struggled to understand the local geology. Hungarian Falls was a critical spot where ideas about the Keweenaw Fault were first formulated.

Above diagram from Lane 1911 integrates the Keweenaw Fault into a regional geologic/tectonic scheme which shows the Lake Superior Syncline (Midcontinent Rift Valley).  Understanding the Keweenaw Fault was important in getting the big picture.

A USGS report published in 1885 first interpreted the fault location at Upper Hungarian Falls (see left). In those diagrams the older, upthrusted lavas and conglomerates are in violet and the sandstones in white.


Area of Hungarian Falls is shaded pink in these diagrams.

Jacobsville SS

Portage Lake Volcanics

Cornwall & Wright, 1956, Geology of Laurium Quadrangle USGS Mineral Investigations Field Studies Map MF 47

Cross section of Keweenaw Fault at Upper Hungarian Falls (Irving & Chamberlin, 1885)

1. The Fault     2. Dam    3. Crossbedding   4. Potholes    5. Plunge Pool   6. Bigger River?    History