Editing Mount Merapi (section)

==Monitoring==
[[File:A selection of instruments used for monitoring volcanoes.jpg|thumb|This image shows some of the instruments deployed by the Deep Carbon Degassing Project in the vicinity of Mount Merapi in 2014.]]
Mount Merapi is the site of a very active volcano monitoring program. [[Seismology|Seismic]] monitoring began in 1924, with some of the volcano monitoring stations lasting until the present. The Babadan (northwest location), Selo (in the saddle between [[Mount Merbabu|Merbabu]] and Merapi), and [[Plawangan]] monitoring stations have been updated with equipment over the decades since establishment. During the 1950s and early 1960s some of the stations were starved of equipment and funds, but after the 1970s considerable improvement occurred with the supply of new equipment. Some of the pre-1930 observation posts were destroyed by the 1930 eruption, and newer posts were re-located. Similarly after the 1994 eruption, the Plawangan post and equipment were moved into [[Kaliurang]] as a response to the threat of danger to the volcanological personnel at the higher point. This volcano is monitored by the [[Deep Earth Carbon Degassing Project]].

The eruption of 1930 was found to have been preceded by a large earthquake swarm. The network of 8 [[seismograph]]s currently around the volcano allow volcanologists to accurately pinpoint the [[hypocentre]]s of tremors and quakes.

A zone in which no quakes originate is found about 1.5&nbsp;km below the summit, and is thought to be the location of the [[magma chamber|magma reservoir]] which feeds the eruptions.

Other measurements taken on the volcano include [[magnetism|magnetic]] measurements and tilt measurements. Small changes in the local magnetic field have been found to coincide with eruptions, and tilt measurements reveal the [[Deformation (volcanology)|inflation]] of the volcano caused when the magma chambers beneath it is filling up.

[[Lahar]]s (a type of [[mudflow]] of pyroclastic material and water) are an important hazard on the mountain, and are caused by [[rain]] remobilizing pyroclastic flow deposits. Lahars can be detected seismically, as they cause a high-[[frequency]] seismic signal. Observations have found that about 50&nbsp;mm of rain per hour is the threshold above which lahars are often generated.