Welcome to Wikipedia,
the free encyclopedia that anyone can edit.
6,502,079 articles in English
From today's featured article

Lassen Peak erupting on May 22, 1915
The geology of the Lassen volcanic area in the U.S. presents a record of sedimentation and volcanic activity in and around Lassen Volcanic National Park in Northern California. Heat from the subduction of tectonic plates has fed scores of volcanoes over at least the past 30 million years, including those in the Lassen volcanic area. Lava flowed over a lahar-based formation to create the lava plateau that the park sits on. About 600,000 years ago, Mount Tehama started to rise in the park's southwest corner. Roughly 27,000 years ago, a lava dome pushed through Tehama's former flank, becoming Lassen Peak. Phreatic (steam-blast) eruptions, lava flows, and cinder cone formations have persisted into modern times, particularly the formation of Cinder Cone and the 1914 to 1921 eruptions of Lassen Peak (eruption pictured). Since the latter eruptions, the only volcanic activity has been from mud pots and fumaroles. Renewed vigorous volcanic activity could threaten life and property in the area. (Full article...)
Did you know ...

Inna Derusova
In the news

Hassan Sheikh Mohamud
On this day

Trevi Fountain
T. Boone Pickens (b. 1928)Lady Gregory (d. 1932)Myrtle Bachelder (d. 1997)
More anniversaries: May 21 May 22May 23
Today's featured picture
This is a high-resolution topographic map of the surface of Mars, colored according to elevation, based on research led by Maria Zuber and David Smith on data collected by the Mars Orbiter Laser Altimeter, an instrument on board the NASA space probe Mars Global Surveyor. North is at the top of the main map, accompanied by two insets for the northern and southern polar regions. Highlands (red and orange) dominate the southern hemisphere of Mars, while lowlands (blue) predominate in the north – a feature known as the Martian dichotomy. Notable large surface features visible on the map include Olympus Mons (the highest mountain on Mars) and the volcanoes of Tharsis in the west, the Valles Marineris to the east of Tharsis, and the Hellas basin in the southern hemisphere.
Map credit: NASA/JPL/USGS; edited by WolfmanSF
Recently featured: Lucy ArbellHeteractis magnifica Supermarine Spitfire
ArchiveMore featured pictures
Other areas of Wikipedia
  • Community portal – The central hub for editors, with resources, links, tasks, and announcements.
  • Village pump – Forum for discussions about Wikipedia itself, including policies and technical issues.
  • Site news – Sources of news about Wikipedia and the broader Wikimedia movement.
  • Teahouse – Ask basic questions about using or editing Wikipedia.
  • Help desk – Ask questions about using or editing Wikipedia.
  • Reference desk – Ask research questions about encyclopedic topics.
  • Content portals – A unique way to navigate the encyclopedia.
Wikipedia's sister projects
Wikipedia is written by volunteer editors and hosted by the Wikimedia Foundation, a non-profit organization that also hosts a range of other volunteer projects:
Wikipedia languages
This Wikipedia is written in English. Many other Wikipedias are available; some of the largest are listed below.
1,000,000+ articles
العربية Deutsch EspañolFrançais Italiano Nederlands日本語 Polski PortuguêsРусский Svenska УкраїнськаTiếng Việt 中文
250,000+ articles
Bahasa Indonesia Bahasa MelayuBân-lâm-gú Български CatalàČeština Dansk EsperantoEuskara فارسی עברית 한국어Magyar Norsk Bokmål RomânăSrpski Srpskohrvatski SuomiTürkçe
50,000+ articles
Asturianu বাংলা BosanskiEesti Ελληνικά Simple EnglishGalego Hrvatski LatviešuLietuvių മലയാളം МакедонскиNorsk nynorsk Shqip Slovenčina​Slovenščina ไทย
Language
View edit history of this page.
Content is available under CC BY-SA 3.0 unless otherwise noted.
Privacy policy
Terms of Use
Desktop
HomeRandom Nearby Log inDonateAbout WikipediaDisclaimers