The volcanic rock could transport Pacific sea organisms to restock the bleached reef off Australia.
Waves hit the coast around the Sunda Strait between the islands of Java and Sumatra on Saturday.
Soputan is on the northern part of Sulawesi island, where a central region was severely damaged by an earthquake and tsunami last Friday.
The latest estimate of property losses far surpasses the 215 structures consumed by lava during more than 30 years of an earlier eruption cycle that began in 1983.
At least 75 are dead and nearly 200 people are missing.
Just a fraction of the victims have been identified so far.
Authorities say lava flows reaching the Pacific Ocean could produce noxious clouds of acid fumes, steam and tiny, glass-like particles.
"Vog," a mix of ash and volcanic smog, rose to 12,000 feet and showered cars with gray dust.
Some 37 buildings have been destroyed and nearly 2,000 people ordered to evacuate in the past 10 days.
The American Red Cross is operating shelters for evacuated residents while the county and Salvation Army provide food and supplies.
The lava continues to claim homes and structures on the Big Island as officials keep track of new fissures.
Officials can't predict when the volcanic threat will die down.
The eruption of the Kilauea volcano on Hawaii’s Big Island has forced nearly 2,000 people to evacuate their homes.
Fissures have opened in the Big Island's Puna district, spewing lava and toxic gases. Scientists say more are likely to appear.
Kilauea volcano on Hawaii's Big Island has come alive with earthquakes and fresh lava flow.
Eight fissures have opened up and spewed lava. At least five homes have been destroyed, but no injuries reported.