Earth Hazards of the Western US

Natural hazards are events that result from natural processes and that have significant impacts on human beings. Extreme weather conditions or geologic activity can cause substantial short-term or long-term changes to our environment. These changes can influence crops, homes, infrastructure, and the atmosphere. The 4.6-billion-year-old Earth has experienced many of these natural changes, and it has always adjusted accordingly.

See Chapter 4: Topography to learn more about the landforms of the Western states.

The Western United States is located at the junction of three tectonic plates: the Pacific, the Juan de Fuca, and the North American. The movement of these plates, even though it occurs on the scale of millimeters per year, makes the Western US a dynamic landscape. The dramatic result is a dizzying assortment of natural hazards such as earthquakes, tsunamis, landslides, and volcanoes. The Pacific plate is subducting under Alaska, creating the volcanoes of the Aleutian Islands. The Juan de Fuca plate is subducting under Washington, Oregon, and Northern California, creating the Cascade volcanoes, and the Pacific plate is grinding past the North American plate along the famous San Andreas Fault. At the same time, the Basin and Range province, which includes nearly the entire state of Nevada, is being stretched and faulted by plate movement. While the motion of all tectonic plates can cause earthquakes, the movement of a subducting plate can cause the world’s largest earthquakes and tsunamis. Tectonic activity lifts the landscape high above sea level, and because uplifted land is subject to the force of gravity, mass wasting processes such as landslides are the inevitable result. These events can be triggered by rain, earthquakes, and coastal or river erosion. The Western US contains rugged landscapes and breathtaking vistas, but with that beauty comes a cost: there are more earthquakes, tsunamis, landslides, and volcanoes in the Western states than in all the other states combined. (While many of these same hazards affect the Hawaiian Islands, there are enough significant differences to warrant discussing Hawai’i separately.)