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Frequently Asked Questions and Answers – Hawaiian Volcanoes and Hazards

Scientists at the USGS Hawaiian Volcano Observatory are often asked questions about various volcanic processes, hazards, and conditions associated with Hawaiian volcanoes. Based upon these questions, we have compiled a list of those most frequently asked with answers provided by geologists and geophysicists who monitor activity and conduct research at the USGS Hawaiian Volcano Observatory.

Answers often include links to resources where you can find additional information. Below is a list of subjects and specific questions. Please click the subject to access the answers.


Mauna Loa

Frequently asked questions about the recent unrest:

  • What is happening on Mauna Loa? 
  • Does and ADVISORY Alert level mean that Mauna Loa is about to erupt?
  • Why do HVO scientists think that a Mauna Loa eruption is NOT imminent at this time?
  • Will eruption precursory signals be obvious in the publicly available monitoring data? 
  • What do the USGS Volcano Alert Levels and Aviation Color Codes mean?
  • Under what circumstances will the Volcano Alert Level for Mauna Loa change? 
  • How will HVO scientists respond to a change in the Volcano Alert Level for Mauna Loa?
  • What can I do to prepare for a Mauna Loa eruption?
  • How can I stay informed about the status of Mauna Loa?
  • How will I find out about a Mauna Loa eruption?
  • How much time will I have to respond to a Mauna Loa eruption? 
  • What kinds of volcanic hazards will a Mauna Loa eruption pose?
  • What are the possible impacts of a Mauna Loa eruption?

General questions about Mauna Loa:

  • What does the name "Mauna Loa" mean?
  • How big is Mauna Loa?
  • Is Mauna Loa an active volcano? Will it erupt again?
  • How often has Mauna Loa erupted?
  • Where on Mauna Loa is an eruption likely to occur?
  • When was the most recent eruption of Mauna Loa?
  • Can HVO scientists forecast a Mauna Loa eruption?
  • What kinds of instruments are used to monitor Mauna Loa and other Hawaiian volcanoes?
  • Is Mauna Loa expected to erupt soon?
  • Are Mauna Loa eruptions similar to Kīlauea eruptions?

Frequently Asked Questions about earthquakes in American Samoa

  • What is happening in American Samoa? 

  • Why are earthquakes happening in American Samoa?  

  • Where are the earthquakes located in the American Samoa earthquake swarm? 

  • Why is it difficult to locate the earthquakes occurring in American Samoa? 

  • Why are there volcanoes in American Samoa, and how often do they erupt? 

  • What is the USGS doing to understand this activity better? 

  • How long do earthquake swarms last? 

  • What could happen, and what hazards might impact American Samoa Islands? 

  • What should I do to protect myself and my family now and if there is an eruption? 

  • How can I stay informed about this activity?  

  • How can I report observations about this activity? 

  • Is it possible that residents will be evacuated? 

Frequently Asked Questions about Kīlauea's Recent Eruption

  • What triggered this eruption? Is this a major or minor event? 
  • Will there be explosions (because of water)? 
  • What do we know about the new lava lake? 
  • Can you tell if the lava is feeding up from the bottom or only flowing down the sides? 
  • Does this activity mean the LERZ will erupt again? 
  • Does lava entering the crater through side fissures indicate the 2008-2018 vent is blocked? 
  • Will the floor of the crater collapse like it did in 2018? 
  • How long before the lava lake reaches the rim of Halemaʻumaʻu? 
  • How can I view the eruption?
  • Why are some areas within Hawai‘i Volcanoes National Park closed to the public?
  • What steps do HVO and NPS staff take to be safe in hazardous areas?
  • Why is it necessary for USGS HVO staff to enter hazardous areas?
  • Is it safe to breathe volcanic gas or vog?
  • Did the M4.4 earthquake on Dec. 20 trigger this eruption? 
  • Is the change in tilt indicative of anything in particular, like intrusion down into the rift zone? Or just because of the release and draining of magma into Halema'uma'u? 
  • Why is there so much gas coming from the crater?  

Frequently Asked Questions about Kīlauea's summit water

  • What was the source of the water in Kīlauea's summit water lake?
  • What did the level, temperature, color, and chemistry of the water in the lake tell us? 
  • What eruption styles are possible at Kīlauea’s summit? 
  • What did the water lake atop Kīlauea mean for future eruptions and hazards at the summit of Kīlauea? 
  • What did HVO doing to monitor the water lake and greater Kīlauea summit area? 

Vog, or volcanic smog

  • What is "vog"? How is it related to SO2 emissions?
  • What controls vog on the Island of Hawai‘i?
  • What health effects are associated with vog?
  • Where can I find results from scientific research or technical data about the effects of vog on human health?
  • Does vog impact plants and animals?
  • Who monitors air quality and vog in Hawai‘i, and where can I find current information?
  • Why are some roads and trails in Hawai‘i Volcanoes National Park closed?
  • What can I do to protect myself from vog?
  • Should I cancel my plans to visit Hawai‘i because of SO2 and vog?
  • How do other communities near active volcanoes deal with SO2 emissions?

Volcanic gas

  • What gases are emitted by Kīlauea and other active volcanoes?
  • Who monitors volcanic gases emitted by Kīlauea?
  • How do HVO scientists measure volcanic gas emissions at Kīlauea?
  • How much sulfur dioxide (SO2) gas comes from Kīlauea?
  • Why do I still smell sulfur when SO2 emissions are low?
  • Will Kīlauea emit high levels of SO2 again?

Lava-flow hazards

  • Who prepared the Lava-Flow Hazard Zone Map for Hawai‘i Island?
  • What does the Lava-Flow Hazard Zone Map show?
  • Are the boundaries between lava-flow hazard zones distinct lines?
  • Why did the USGS prepare the Lava-Flow Hazard Zone Map?
  • If the map was made for general planning purposes, why were so many building permits issued and so much construction allowed in Zones 1 and 2?
  • How were the lava-flow hazard zones determined?
  • The Lava-Flow Hazard Zone Map is 20 years old. Is it still accurate?
  • Will the Lava-Flow Hazard Zone Map be revised?
  • How can Hawai‘i Island residents determine the lava-flow hazard zones in which their properties are located?
  • How and why is the Lava-Flow Hazard Zone Map used by home insurance or mortgage companies?
  • What can a homeowner do if a company uses the map to set elevated insurance or mortgage rates?
  • What can a homeowner do if a lava-flow hazard zone is used as a reason for non-renewal of a home owner's insurance policy?
  • How does location near a rift zone affect lava-flow hazards?
  • Why is an area freshly covered by lava designated as Zone 2, while another area not recently threatened by lava is designated as Zone 1?
  • As a specific example, why is Kalapana in Zone 2, while Leilani Estates in Zone 1?
  • Have lava-flow hazard zone maps been prepared for other Hawaiian Islands?
  • Where can Maui residents find lava-flow hazard zone information?
  • How do Maui lava-flow hazard zone numbers compare to those on Hawai‘i Island?
  • Where can I read more about lava-flow hazard zones in Hawai‘i?

Volcanic ash and other tephra

  • What is volcanic ash?
  • When has Kīlauea erupted volcanic ash?
  • Who monitors ashfall from Kīlauea?
  • How much ash is Kīlauea currently erupting?
  • Does volcanic ash pose hazards to human health?
  • What other hazards are associated with volcanic ash?
  • What can I do to minimize the impacts of volcanic ash?