Hi Chris. To the best of my knowledge all of the Cascade volcanoes are eruptive in nature such as what has been seen at Mount Saint Helens with but one exception. This exception is Medicine Lake Volcano located in northern California. The volcano is located in a zone of east-west crustal extension east of the main axis of the Cascade Range. It is this extension that may account for the eruptions seen at Medicine Lake.

The Medicine Lake shield volcano is a sleeping giant. It is the largest volcano in the Cascade Range filling up the entire southern skyline. It has been erupting off and on for half a million years. The eruptions were gentle rather than explosive like Mount St. Helens, coating the volcano's sides with flow after flow of basaltic lava. This created a shield-shaped mountain approximately 150 miles around the base and 7900 feet high. Medicine Lake is part of the old caldera, a bowl-shaped depression in the mountain. It is believed that the Medicine Lake Volcano (MLV) is unique in that it has many small magma chambers rather than one large one.

Medicine Lake volcano (MLV) is a Pleistocene and Holocene shield volcano located in the Cascade Range, east of the main arc and northeast of Mount Shasta. Lavas from MLV cover about 2000 square kilometers. They range in composition from basalt through rhyolite and include both tholeiitic and calc-alkaline types.

Basalt and basaltic andesite dominate the lower flanks of MLV. Higher on the volcano, basaltic lavas are mostly absent, andesite dominates, and high-silica lavas are present, including the spectacular late Holocene rhyolites of Glass Mountain and Little Glass Mountain. Volume of the volcano is estimated at 600 cubic kilometers, larger than Mount Shasta, which is the largest of the Cascade stratocones. The highest point on the rim of MLV's caldera is 7,913 feet. Lava flows reach elevations as low as 3360 feet although most lavas are found above 4100 feet, the approximate elevation of the surrounding Modoc Plateau.

Over the last 500,000 years, the volcano has erupted periodically, sending very fluid lava over a wide area and building a large, gently sloped mountain. No field evidence has been found to substantiate a report of an eruption in 1910.

Formation of lava tubes was the result of very hot fluid lava issuing from cracks or fissures on moderate slopes. As the lava flowed it began to cool and solidify on the top and sides. Once the eruption ceased, the tube emptied and drained, and a new lava tube cave was born. As the rock cooled, the inner surface of the tube cracked and collapsed, producing openings to the surface.

At the last count, there are 435 known lava tube caves within the boundaries of Lava Beds National Monument. The caves vary widely in size and length. Some caves are so small that a would-be explorer must crawl the entire length, while some caves are more than 60 feet in diameter. Two dozen of the caves have been developed for public use, with ladders or steps for access and cleared paths through rubble fields. Most of the "public" caves are located along the Cave Loop Road near the Visitor Center.

As absolute must when going into the caves is a hard hat. I have more then one bump on the head to attest to the fact that a hard hat is good insurance. I always carried two flashlights with extra batteries for both whenever I went into the caves. I also found that a good pair of leather gloves is good for protecting the hands. I have even seen some people wearing kneepads. Helps when you have to crawl and there are many places where you will have to crawl.

Don’t know if this would be of any interest to you, but in August of this year my partner in crime and I took a tour of the Mount Lassen area. He has a home in Susanville so it made it easy for us to tour the area. While we were there we learned that the water from the hot springs is getting hotter as well as the mud pots that can be found in the area. The cause at this time isn’t known. The last eruption in the area was in 1917 and it was much in the same way as Mount Saint Helens. The destruction of that eruption can still be seen although not as spectacular as Mount Saint Helens. Take Care…Don in creepy town

• Medicine Lake Volcano