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Lassen Volcanic National Park is a United States National Park in northeastern California. The dominant feature of the park is Lassen Peak, the largest plug dome volcano in the world and the southern-most volcano in the Cascade Range. Lassen Volcanic National Park started as two separate national monuments designated by President Theodore Roosevelt in 1907: Cinder Cone National Monument and Lassen Peak National Monument.〔(【引用サイトリンク】title=The Story of the Antiquities Act ) Chapter 8: The Proclamation of National Monuments Under the Antiquities Act, 1906–1970〕 The source of heat for volcanism in the Lassen area is subduction off the Northern California coast of the Gorda Plate diving below the North American Plate. The area surrounding Lassen Peak is still active with boiling mud pots, stinking fumaroles, and churning hot springs. Lassen Volcanic National Park is one of the few areas in the world where all four types of volcano can be found (plug dome, shield, cinder cone, and strato).〔(【引用サイトリンク】publisher=California Academy of Sciencies )〕 The park is accessible via State Routes SR 89 and SR 44. SR 89 passes north-south through the park, beginning at SR 36 to the south and ending at SR 44 to the north. SR 89 passes immediately adjacent the base of Lassen Peak. There are a total of five vehicle entrances to the park: the north and south entrances on SR 89, and unpaved roads entering at Drakesbad and Juniper Lake in the south, and Butte Lake in the northeast. The Park can also be accessed by trails leading in from Caribou Wilderness to the east, as well as the Pacific Crest Trail, and two smaller trails leading in from Willow Lake and Little Willow Lake to the south. A large lodge (the Lassen Chalet) with concession facilities formerly was located near the south-west entrance, but was demolished in 2005. A new, full-service visitor center was constructed in the same location, and opened to the public in 2008. Near the old lodge location was also located Lassen Ski Area, which ceased operation in 1992; all infrastructure has been removed. ==History== Native Americans have inhabited the area since long before white settlers first saw Lassen. The natives knew that the peak was full of fire and water and thought it would one day blow itself apart.〔''Geology of National Parks'', pp. 542–46.〕 White immigrants in the mid-19th century used Lassen Peak as a landmark on their trek to the fertile Sacramento Valley. One of the guides to these immigrants was a Danish blacksmith named Peter Lassen, who settled in Northern California in the 1830s. Lassen Peak was named after him.〔 Nobles Emigrant Trail was later cut through the park area and passed Cinder Cone and the Fantastic Lava Beds. Inconsistent newspaper accounts reported by witnesses from 1850 to 1851 described seeing "fire thrown to a terrible height" and "burning lava running down the sides" in the area of Cinder Cone. As late as 1859, a witness reported seeing fire in the sky from a distance, attributing it to an eruption. Early geologists and volcanologists who studied the Cinder Cone concluded the last eruption occurred between 1675 and 1700. After the 1980 eruption of Mount St. Helens, the United States Geological Survey (USGS) began reassessing the potential risk of other active volcanic areas in the Cascade Range. Further study of Cinder Cone estimated the last eruption occurred between 1630 and 1670. Recent tree-ring analysis has placed the date at 1666. The Lassen area was first protected by being designated as the Lassen Peak Forest Preserve. Lassen Peak and Cinder Cone were later declared as U.S. National Monuments in May 1907 by President Theodore Roosevelt.〔''Geology of U.S. Parklands'', p. 154.〕 Starting in May 1914 and lasting until 1921, a series of minor to major eruptions occurred on Lassen. These events created a new crater, and released lava and a great deal of ash. Fortunately, because of warnings, no one was killed, but several houses along area creeks were destroyed. Because of the eruptive activity, which continued through 1917, and the area's stark volcanic beauty, Lassen Peak, Cinder Cone and the area surrounding were declared a National Park on August 9, 1916.〔 The Main Park Road was constructed between 1925 and 1931, just 10 years after Lassen Peak erupted. Near Lassen Peak the road reaches , making it the highest road in the Cascade Mountains. It is not unusual for of snow to accumulate on the road near Lake Helen and for patches of snow to last into July. In October 1972, a portion of the park was designated as Lassen Volcanic Wilderness by the US Congress (Public Law 92-511). The National Park Service seeks to manage the wilderness in keeping with the Wilderness Act of 1964, with minimal developed facilities, signage, and trails. The management plan of 2003 adds that, "The wilderness experience offers a moderate to high degree of challenge and adventure."〔(【引用サイトリンク】format=PDF )〕 In 1974, the National Park Service took the advice of the USGS and closed the visitor center and accommodations at Manzanita Lake. The Survey stated that these buildings would be in the way of a rockslide from Chaos Crags if an earthquake or eruption occurred in the area.〔 An aging seismograph station remains. However, a campground, store, and museum dedicated to Benjamin F. Loomis stands near Manzanita Lake, welcoming visitors who enter the park from the northwest entrance. After the Mount St. Helens eruption, the USGS intensified its monitoring of active and potentially active volcanoes in the Cascade Range. Monitoring of the Lassen area includes periodic measurements of ground deformation and volcanic-gas emissions and continuous transmission of data from a local network of nine seismometers to USGS offices in Menlo Park, California.〔USGS: Volcano Hazards of the Lassen Volcanic National Park Area, California〕 Should indications of a significant increase in volcanic activity be detected, the USGS will immediately deploy scientists and specially designed portable monitoring instruments to evaluate the threat. In addition, the National Park Service (NPS) has developed an emergency response plan that would be activated to protect the public in the event of an impending eruption. The National Park Service counts visitors to Lassen National Park by using in-road inductive loops at all the vehicle entrances to count vehicles entering the park. Buses and other non-reportable vehicles are subtracted from the vehicle counts and then a persons-per-vehicle multiplier of 3 is multiplied by the vehicle number.〔(【引用サイトリンク】title=Public Use Reporting and Counting Instructions )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lassen Volcanic National Park」の詳細全文を読む スポンサード リンク
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