Copper Country Shaken
On July 26, 1905, the quiet towns of Michigan’s Keweenaw Peninsula experienced a startling natural event that left a lasting mark on the region’s history. The Keweenaw Peninsula earthquake, estimated at VIII on the Mercalli Intensity Scale—equivalent to about a 5.0 to 5.9 on the Richter Scale—rattled the area, toppling chimneys, breaking windows, and sending tremors far beyond the immediate vicinity. Residents from Calumet to Copper Harbor and as far east as Marquette felt the shaking, causing such fear that many copper miners refused to descend into the mines for their night shifts.
The 1905 quake was not an isolated incident. Between 1902 and 1909, over 20 earthquakes shook Michigan’s Upper Peninsula, with a notable swarm of tremors crisscrossing the region. Earlier that year, on March 13, a milder quake of approximately 3.8 magnitude shook Menominee County, initially blamed on “air blasts” inside mines.
Felt and Heard for Miles
But the July 26 quake was by far the most powerful and memorable. It began with a tremendous boom heard as far away as Marquette, followed by roughly ten seconds of intense shaking. In Calumet, Lake Linden, and Hancock, chimneys fell, windows shattered, and houses even shifted slightly off their foundations. The miners working deep underground, some as far down as the 49th level of the Quincy Mine, felt the tremors distinctly. The fear and damage were so significant that some residents decided to leave the Keweenaw Peninsula altogether.
At the time, scientists and local experts speculated about the cause. Fred W. McNair, president of the Michigan College of Mines (now Michigan Technological University), suggested the quakes were due to “an uplift of the land.” Geologist William Herbert Hobbs agreed in a 1911 report. However, modern interpretations lean towards mine collapses and rock bursts as the likely triggers, given the extensive mining activity in the area.
The Fault Line
The Keweenaw Peninsula sits atop the Keweenaw Fault, a significant reverse fault stretching over 100 miles. This fault thrust ancient lava flows onto older sedimentary rock formations and is tied to a deep geologic history involving the Midcontinent Rift System and the Grenvillian orogeny. Although seismic events are rare today, the early 20th-century quakes remain a fascinating chapter in Michigan’s geologic and mining heritage.
One of the more dramatic accounts came from Captain Harry Gunderson of the steamer Henry Steinbrenner on April 19, 1906. Near Eagle Harbor, his ship suddenly quivered and rocked without warning, the lake’s surface churning, and the compass needle spinning wildly—clear evidence that seismic activity could impact even the waters of Lake Superior.
Though the tremors of 1905 caused significant local alarm, they also remind us of the dynamic natural forces at play beneath Michigan’s Copper Country. Whether from deep earth movements or mining-related collapses, these quakes shaped the lives and landscapes of the region, forever linking geology and human endeavor.
Learn more about the rich history of the Western Upper Peninsula.
