NSS Convention ~ July 25-30, 2021

California geologic map

Regional Geology - California's North

The complex geologic forces in northern California have created a region with exceptionally complicated and challenging topography. On the west, the coastal mountain ranges run along the Pacific from the Oregon boundary to Marin County. The state's northern boundary runs through the Klamath and Cascade Mountains and the Modoc Plateau.

On this website, we've tried to feature the dominant geologic landmarks of the area around Weed, California. Many of these highlights may be visited by easy day trips from the convention site. We're also offering two distinctly different geology field trips that will explore these areas in much greater detail.


At an elevation of 14,179 feet, Mt. Shasta towers above the local terrain. Its summit is only 10 miles from the convention site. Local inhabitants have held this impressive mountain in reverence since they first passed through and settled between 11,000 and 7,000 years ago. Mt. Shasta is the second highest peak and the most voluminous stratovolcano in the Cascade Range of the northwest US.


Medicine Lake volcano is situated just east of the Cascade Volcanic Arc axis in northern California's high desert, just 35 miles northeast of Mount Shasta. Also known as the Medicine Lake Highlands, this volcanic region covers a total area of about 850 square miles, extending approximately 50 miles north-south and 30 miles east-west. A shallow, but wide caldera basin containing its namesake lake is located at the summit of the volcano.


Lassen Volcanic National Park is in northern California. It's rich in hydrothermal sites like Bumpass Hell, with its acres of bubbling mud pots. The summit of Lassen Peak Volcano offers views over the surrounding wilderness. Nearby, the Devastated Area is littered with lava rocks from its last eruption.


The explosive geology of the Cascade Volcanic Arc has created a unique environment for cave exploration. Literally hundreds of caves exist within easy distance of Weed, California. These caves range from a few feet to several thousand feet in length. Lava tube caves were formed by flowing lava which moved beneath the hardened surface of a lava flow. Tubes drain lava from a volcano during an eruption.


The McCloud Limestone is a cavernous formation of Lower Permian age located in the region near Shasta Lake in Northern California. The formation contains the commercial cave, Lake Shasta Caverns. Often, the limestone outcrops in prominent cliffs along the lake and rivers, and the terrain is very rugged, covered largely with trees and brush.


The Cascade Volcanic Arc is a series of volcanoes in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California - a distance of well over 700 miles. The arc formed due to subduction along the Cascadia subduction zone. Population in the region exceeds 10 million - all of whom could be potentially affected by volcanic activity and great subduction-zone earthquakes along the arc.

Learn More About Volcanoes!