A geologist says it’s not uncommon for coal to settle on Queensland’s beaches, and you could soon add Tonga’s volcanic eruption pumice to your beach debris collection.
Key points:
- Pebble ponds have been floating on the currents to Australia since the eruption of the Tonga volcano
- Currents and tides affect exactly where the porous stones will be washed
- The pumice stone could carry mollusks and other invertebrate animals
Maree Corkeron, a senior professor of earth and environmental sciences at James Cook University, said the remnants of the eruption of the Hunga Tonga-Hunga Ha’apai volcano in Tonga in January are expected to reach Australian coasts this year.
“We often have pumice stone washing on the lines and people walk around it without really thinking about it,” Dr. Corkeron said.
Dr. Maree Corkeron says the pumice stone in Tonga’s volcano could be found in about six months. (Provided by: Maree Corkeron)
Corkeron said it had to do with the proximity of North Queensland to the volcanic hot spot known as the Pacific Ring of Fire, or the Circum-Pacific Belt, a 40,000-mile-long arc that hosts 75 percent of the volcanoes. of the Earth.
North Queensland beaches that were windy, or low current, from the Ring of Fire were more likely to see pumice.
Dr. Corkeron said what was dragged into the sand really depended on activity in the Pacific Ocean.
“It’s a combination of our location, tectonics and global trade winds,” he said.
“Local currents and wind conditions will determine exactly where the pumice ends.”
Floating stone
Corkeron said that where continental oceanic plates were colliding with each other and generating volcanoes, such as the one that exploded in Tonga, “they generate large amounts of ash and rocky material.”
Pumice is formed when volcanic matter reaches the water and cools rapidly.
“While the structure is solid, there’s a lot of space between these spicules … so it’s very light and floats on top of the ocean,” he said.
The material often clumps together and forms large ponds.
“Sometimes these ponds are hundreds of miles in diameter,” Dr. Corkeron said.
Maree Corkeron picked up this pumice stone in 2014. (Supplied by Maree Corkeron)
The waves break the pumice stone, and when it reaches the ground it is often the size of a pebble.
But it could be much bigger.
“I have a few specimens that I have collected on the beach of Alva [near Ayr] maybe 10 or 15 years ago they were [about] the size of a football, “Dr. Corkeron said.
“The whole beach was covered with large boulders.”
But not all the cobblestones would reach the ground.
“When the pumice stone approaches our shores, it may have been floating for many months and caught many hitchhikers,” he said.
Mollusks, bryozoans (aquatic invertebrates) and even coral are known to grow on floating debris, increasing the weight of the pumice stone and causing part of it to sink.
“It also acts as a very important mechanism for rafting and dispersing these marine organisms,” he said.
When the pumice stone begins to crawl on the ground, it could be covered with marine life. (ABC North Qld: Zilla Gordon)
Dr. Corkeron said she expects to see remnants of Hunga Tonga-Hunga Ha’apai in six to seven months.
“Because there is a lot of underwater volcanism in the western Pacific related to the subduction of oceanic plates and associated with island arcs like Tonga and Vanuatu, we have a lot of pebbles on the beaches of eastern Australia,” he said.
“Studies to track pumice after eruptions are based on tracking beaches for pumice stranding, near the eruption, and then across the Pacific Ocean to on the beaches of Eastern Australia for a few years after the event. “
Compacted marine life
When Nicola Carlisle moved to North Queensland two years ago, she was amazed at what she discovered on the beaches of Townsville.
Mrs. Carlisle said she regularly watched black lumps on the beach and noticed that others were ordering the rubble to be taken away.
“I started to notice that in the last few weeks there were more and more and some were getting pretty big,” he said.
On her last walk, Mrs. Carlisle grabbed one and was baffled.
“It was like a soft rock … and when I smelled my fingers it smelled like diesel or gasoline,” he said.
“It didn’t smell like something the ocean had done.”
Dr. Corkeron said that although coal can be found on our beaches, it was more likely to be sediment.
Nicola Carlisle found what he thought was washed coal on a Townsville beach. (Provided by: Nicola Carlisle)
As marine biota, algae, and organic matter die, it settles to the bottom of the ocean and is compressed by sand for millions of years.
“[It] accumulates in the bay over a long period of time. It has been buried for hundreds of thousands of years, “said Dr. Corkeron.
“And if there is no oxygen in the environment, it will degrade in a way that creates an odor of oil.”
Corkeron said the increase in sediment on the beaches could also be due to a $ 232 million canal improvement in Townsville Harbor.
Coal differs from compressed sediment by fracturing normally along its dowel lines rather than collapsing.
On the beaches of Townsville you can find handfuls of compressed sediment like coal, or just coal, dragged. (ABC North Qld: Zilla Gordon)
“[The coal] it could be covered with barnacles and some have things growing in it. Anything that floats in the ocean is a nice little host for the biota to settle in … so you may find that there are small pieces of mollusk, ”Dr. Corkeron said.
Two hundred miles south is one of Australia’s largest ports, Abbott Point, and the coal of ships often went to the beaches of North Queensland.
“Technically, you could burn it if you wanted to,” Dr. Corkeron said.