The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States. Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years. Heat from these subducting plates has fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years and is also responsible for activities in the Lassen volcanic area. Between 2 and 4 million years ago, volcanic-derived mud flows called lahars streamed down several major mountains that included nearby but now extinct Mount Yana and Mount Maidu to become the Tuscan Formation. Phreatic eruptions, dacite and andesite lava flows along with cinder cone formation have persisted into modern times. Most notable of these is the 18th century formation of Cinder Cone and the 1914 to 1921 eruption of Lassen Peak. The only activity since then has been the constant bubbling of mud pots and steaming of fumaroles from the various geothermal areas in Lassen Volcanic National Park. However, there exists a potential for renewed vigorous volcanic activity that could threaten life and property in the area.

Read the rest of this article: http://en.wikipedia.org/wiki/Geology_of_the_Lassen_volcanic_area

_______________________________ Today's selected anniversaries:

565: Justinian the Great deposed Eutychius, Patriarch of Constantinople, after he refused the Byzantine Emperor's order to adopt the tenets of the Aphthartodocetae, a sect of Monophysites. (http://en.wikipedia.org/wiki/Patriarch_Eutychius_of_Constantinople)

1863: The January Uprising, the longest Polish, Belarusian and Lithuanian uprising against the Russian Empire, broke out, originally as a spontaneous protest by young Poles against conscription into the Russian Army. (http://en.wikipedia.org/wiki/January_Uprising)

1879: Anglo-Zulu War: In the greatest British military defeat at the hands of native forces in history, Zulu forces of King Cetshwayo fought to a pyrrhic victory at the Battle of Isandlwana in Isandlwana, South Africa. (http://en.wikipedia.org/wiki/Battle_of_Isandlwana)

1901: After holding the title Prince of Wales for six decades, King Edward VII ascended to the British throne, replacing Queen Victoria whose death ended her reign that lasted 63 years and seven months, longer than any other British monarch. (http://en.wikipedia.org/wiki/Edward_VII_of_the_United_Kingdom)

1973: The U.S. Supreme Court delivered its landmark legal decision in Roe v. Wade, striking down laws restricting abortion during the first six to seven months of pregnancy. (http://en.wikipedia.org/wiki/Roe_v._Wade)

_____________________ Wiktionary's Word of the day:

genuflect: To bend the knee, as in servitude or worship; grove. (http://en.wiktionary.org/wiki/genuflect)

_____________________ Wikiquote of the day:

So, we'll go no more a roving So late into the night, Though the heart be still as loving, And the moon be still as bright. For the sword outwears its sheath, And the soul wears out the breast, And the heart must pause to breathe, And love itself have rest. -- George Gordon, Lord Byron (http://en.wikiquote.org/wiki/Lord_Byron)