Eruption at the Lower East Rift Zone continues and lava has now reached the ocean to the southwest. This is causing additional hazards for the population of Hawai'i.

_{Channelized lava from fissure 16-20 making its way towards the ocean.
volcanoes.usgs.gov}

_{Map of activity at the East Rift Zone from May 21st.
volcanoes.usgs.gov}

The video below was taken by the USGS on the morning of the 21st and shows a flight over the fissure 20 complex. You can see intense fountains erupting from the fissures. Then the video pans out along the two lava channels that flow all the way into the ocean. At the very end of the video you can see the white plume created by the entry of lava into seawater:

_{original video at volcanoes.usgs.gov}

Lava entering the ocean creates a distinctive set of hazards. People trying to watch this spectacle in person often end up injured if not dead.

Current hazard at hand

The primary hazard that puts the population at risk is the white plume that is created where lava meets seawater.

As hot lava boils cool seawater, a series of chemical and physical reactions create a mixture of condensed, acidic steam, hydrochloric acid gas, and tiny shards of volcanic glass. Blown by wind, this plume creates a noticeable downwind haze, known as "laze" (short for lava haze) (volcanoes.usgs.gov)

Unfortunately, the trade winds are travelling from the southeast, carrying material onto the island.
The laze can cause skin and eye irritation, as well as breathing difficulties.

_{Fissure 20 lavas reaching the ocean forming a white plume.
volcanoes.usgs.gov}

Other Ocean Entry Hazards

In addition to the immediate dangers by laze, other hazards arise when lava flows directly into the ocean.

Lava deltas collapse

Lava deltas form where lava builds up along the shore. The edge of the Hawaiian islands are characterized by steep slopes, which are composed of loose and unstable lava fragments. As the delta grows over time, its weight increases. This weight can cause the underlying material to shift, causing the lava flows on top to sink or collapse. Lava deltas can also be quickly swept away into the ocean by submarine landslides. The speed and extend of delta collapses varies drastically, from spontaneous events to long lasting events that cover the entire delta or only small parts of it.

They generally do not really represent a safe space to stand on, which does not hinder people to try. A warning system has been implemented by Hawai‘i Volcanoes National Park, collapses can still come as a surprise. In 1993 a delta collapse caused the death of a photographer standing on the delta itself an injured more than a dozen others.

_{Sketch showing the progressive buildup of a lava delta, forming lava flows (brown) on a foundation of loose lava fragments (white).
volcanoes.usgs.gov}
The collapse of a lava delta can cause additional threats of which the main ones are:

Explosions triggered by delta collapse

The collapse of a lava delta creates room that will consequently be filled by the surrounding ocean water. The mixing of hot lava (>1000 °C) and seawater will create steam driven explosions. These explosions have an incredible force and are able to hurl large rocks out of the collapse center. Rock fragments larger than a meter have been found as far away as 250 m from active lava deltas. Smaller fragments can be transported even further increasing the danger zone significantly.

Wave generation through delta collapse

The force created by a collapsing delta also has immediate effects on the water surrounding it. The hot water gets pushed away creating waves of hot water splashing onto the shore. Large waves coming from the ocean can also travel across the superhot lava of an active delta and get heated to boiling temperatures on their way to the shore. The waves can cause second degree burns if you are unfortunate and get caught by one.
Of course, the effects of waves and explosions are not travelling just on land but have the same effect directed towards the ocean. Here they are a potential threat to boats that swim next to the delta

_{Explosion and wave generation triggered by delta collapse.
volanoes.usgs.gov}

Previous Posts

Hawaiian volcanoes - Part 1: Introduction
Hawaiian volcanoes - Part 2: The Hawaiian Hotspot
Hawaiian volcanoes - Part 3: A growing volcano
Hawaiian volcanoes - Part 4: The Rejuvenation Stage
Hawaiian volcanoes - Part 5: Evolution to Atolls and Seamounts
Hawaiian volcanoes - Part 6: Mythology vs Geology
Hawaiian volcanoes - Part 7: Recent eruptions
Hawaiian volcanoes - Part 8: Volcano Monitoring
Hawaiian volcanoes - Part 9: Predicting Eruptions
Hawaiian volcanoes - Part 10: Volcanic Air Pollution
Hawaiian volcanoes - Part 11: Volcanoes falling apart… from Landslides and Tsunamis
Hawaiian volcanoes - Part 12: Benefits of Volcanoes
Hawaiian volcanoes - Part 13: The Double Volcano Chain
Hawaiian volcanoes - Part 14.1: Current eruption of Kīlauea
Hawaiian volcanoes - Part 14.2: Update on the current eruption of Kīlauea
Hawaiian volcanoes - Part 14.3: Ongoing eruption of Kīlauea

References

• https://www.usgs.gov/news/k-lauea-volcano-erupts
• https://volcanoes.usgs.gov/observatories/hvo/hawaii_ocean_entry.html
• https://volcanoes.usgs.gov/volcanoes/kilauea/status.html
• https://volcanoes.usgs.gov/volcanoes/kilauea/kilauea_multimedia_15.html
• https://volcanoes.usgs.gov/volcanoes/kilauea/multimedia_maps.html