Final answer:
The Madison River Canyon landslide in Montana was triggered by erosion by rivers, excess weight, and earthquakes.
Step-by-step explanation:
The Madison River Canyon landslide in Montana was triggered by a combination of factors, including erosion by rivers, excess weight, and earthquakes. Erosion by rivers can create over-steepened slopes, while excess weight, such as accumulation of rain or snow, can stress weak slopes to failure. Additionally, earthquakes of magnitude 4.0 and greater have been known to trigger landslides. In the case of the Madison River Canyon landslide, it is likely that these factors collectively contributed to the slope failure and subsequent landslide.