Early reports Captain James Cook saw Mt. Redoubt during the summer of 1778, describing it as "emitting a white smoke but no fire which made some think it was no more than a white thick cloud such as we have frequently seen on the Coast, for the most part appearing on the sides of hills and often extends along a whole range and at different times falls or rises, expands or contracts itself and has a resemblance to Clouds of white smoke. But this besides being too small for one of those clouds, remained as it were fixed in the same spot for the whole time the Mountain was clear which was above 48 hours." However, several sources call this a "discredited eruption". In 1819, smoke was observed at the mountain. However, this is often not recorded as an eruption as the information was insufficient to identify it as such. Similarly, in 2003, a blowing cloud of snow was mistaken by an employee of the
ConocoPhillips Building in Anchorage for an
ash plume. Possible steam-vapor let off was observed in 1933 at the mountain.
1881 There was apparently an eruption described as "to the eastward, Redoubt Volcano, high, is constantly smoking, with periods of exaggerated activity. Fire has been seen issuing from its summit far out at sea. A great eruption took place in 1881, when a party of native hunters half-way up its slopes were overwhelmed by a lava-flow and only two escaped." However, this eruption is not well documented by other sources.
1902 The volcano erupted rather abruptly in 1902, spewing out ash from January 18 to June 21 in the year. A local newspaper stated, "Word has just been received that Redoubt, one of the volcanoes at Cook's Inlet had an eruption on January 18, and the country for around was covered with ashes and lava. The news comes from
Sunrise, but nothing definite has been ascertained as to whether any damage was done, for no boats have as yet been in the neighborhood of the volcano." There were many other news reports on the eruption, one describing the eruption as "a terrific earthquake which burst the mountain asunder leaving a large gap," which could possibly suggest the crack formation in the volcano's crater, however, it is unlikely. Supposedly, the volcano was ejecting "flames" from its crater, and the eruption terrified natives in the area. Newspapers seemed to suggest that the ash had traveled for more than , reaching the opposite side of the
Cook Inlet.
1989–1990 (to a height of about ) from Redoubt Volcano as viewed to the west from the
Kenai Peninsula The volcano erupted on December 14, 1989, and continued to erupt for over six months. Since lahars were produced repeatedly, scientists realized that they could use these to analyze a trial period for a newly developed device proposed to measure the movement of rocks against each other. This device, now known as an Acoustic Flow Monitor, alerts nearby stations to possible lahars. Damage from the eruption was estimated at $160 million, the second costliest volcanic eruption in United States history.
2009 Pre-eruption Anomalous gas emissions were noticed on the volcano starting in July 2008, with a noticeable smell of
hydrogen sulfide.
Precursor earthquakes started on September 28, 2008. By January 31, earthquakes increased to several per hour, and a
large hole in the glacier on the side of the mountain was spotted. Scientists began to monitor seismic data from the mountain twenty-four hours a day in an effort to warn people in nearby communities. A fly over conducted by the AVO detected "significant steaming from a new melt depression at the mouth of the summit crater near the vent area of the 1989-90 eruption." Throughout February, seismic tremors, excess gas, and new
fumaroles were observed at the volcano. Surface rock temperatures were measured as high as . On March 15, a gas measurement flight observed a small explosion followed by a steam plume.
Large scale eruptions begin thrown from the volcano in 2009 is seen on display at the
Anchorage Museum in March 2011. Mount Redoubt erupted explosively late in the evening of March 22, 2009. The
Mat-Su Valley,
Anchorage,
Valdez and large portions of the
Kenai Peninsula all received coatings of
tephra. A lava dome started to grow after an explosion on April 4, 2009. The lava dome ceased to grow by July 2009. The flood was caused by an avalanche of snow mixed with 2009 eruption material. ==Climate==