<p><strong><em>This story is part of a <a href="http://news.nationalgeographic.com/news/energy/">special series</a> that explores energy issues. For more, visit <a href="http://www.greatenergychallenge.com">The Great Energy Challenge</a>.</em></strong></p><p>A beachgoer holds a solidified piece of oil, or "tarball," which washed up on <a id="w2qz" title="Dauphin Island, Alabama (map)" href="http://maps.nationalgeographic.com/map-machine#s=r&amp;c=30.30531763797613, -87.99705505371094&amp;z=10">Dauphin Island, Alabama (map)</a>, in a photo taken on Saturday.</p><p>Tar balls found on the island are believed to be from the massive <a id="tloz" title="Gulf of Mexico oil spill" href="http://news.nationalgeographic.com/news/gulf-oil-spill-news/">Gulf of Mexico oil spill</a>, according to "comparison of the major biomarker indices" carried out by <a id="sfzc" title="Louisiana State University" href="http://info.envs.lsu.edu/">Louisiana State University</a> for the <a id="pblc" title="National Oceanic and Atmospheric Administration" href="http://www.noaa.gov/">National Oceanic and Atmospheric Administration</a>. The oil leaks began when the <a id="l10l" title="BP" href="http://www.bp.com/bodycopyarticle.do?categoryId=1&amp;contentId=7052055">BP</a>-leased <em>Deepwater Horizon</em> oil rig exploded and sank last month.</p><p>Tarballs are common byproducts of oil spills, said <a id="f438" title="Ronald Kendall" href="http://www.tiehh.ttu.edu/ronald_kendall.html">Ronald Kendall</a>, an environmental toxicologist at Texas Tech University. The sticky masses can form when ocean waves concentrate surface oil slicks into clumps, which then wash ashore.</p><p>The tar balls represent a risk to wildlife, Kendall added: They're "not as toxic or as big a problem as a sheen of oil that gets on feathers or fur, but they can still be toxic if swallowed." (See <a id="clw_" title="pictures of ten animals at risk due to the Gulf oil spill" href="http://www.tiehh.ttu.edu/ronald_kendall.html">pictures of ten animals at risk due to the Gulf oil spill</a>.)<br><br><em>—Ker Than</em></p>

Gulf Oil Spill "Tarball"

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.

A beachgoer holds a solidified piece of oil, or "tarball," which washed up on Dauphin Island, Alabama (map), in a photo taken on Saturday.

Tar balls found on the island are believed to be from the massive Gulf of Mexico oil spill, according to "comparison of the major biomarker indices" carried out by Louisiana State University for the National Oceanic and Atmospheric Administration. The oil leaks began when the BP-leased Deepwater Horizon oil rig exploded and sank last month.

Tarballs are common byproducts of oil spills, said Ronald Kendall, an environmental toxicologist at Texas Tech University. The sticky masses can form when ocean waves concentrate surface oil slicks into clumps, which then wash ashore.

The tar balls represent a risk to wildlife, Kendall added: They're "not as toxic or as big a problem as a sheen of oil that gets on feathers or fur, but they can still be toxic if swallowed." (See pictures of ten animals at risk due to the Gulf oil spill.)

—Ker Than

Photograph by Brian Snyder, Reuters

Gulf Oil Spill Pictures: Oil, Tarballs Hit Beaches

The Gulf of Mexico oil spill is likely behind the sticky tarballs and dead dolphins washing up on U.S. beaches, experts say.

Read This Next

The most ancient galaxies in the universe are coming into view
‘Microclots’ could help solve the long COVID puzzle
How Spain’s lust for gold doomed the Inca Empire

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet