What are Tar Balls and How Do They Form?

Tar balls, the little, dark-colored pieces of oil that

stick to our feet when we go to the beach, are actually 

remnants of oil spills. When crude oil (or a heavier 

refined product) floats on the ocean surface, its physical

characteristics change. 

During the first few hours of a spill, the oil spreads

into a thin slick. Winds and waves tear the slick into

smaller patches that are scattered over a much wider area.

Various physical, chemical, and biological processes

change the appearance of the oil. These processes are

generally called “weathering.”

Initially, the lighter components of the oil evaporate

much like a small gasoline spill. In the cases of heavier

types of oil, such as crude oil or home heating oil, much

of the oil remains behind. At the

same time, some crude oils mix

with water to form an emulsion

that often looks like chocolate

pudding. 

This emulsion is much thicker

and stickier than the original oil.

Winds and waves continue to

stretch and tear the oil patches into

smaller pieces, or tar balls. While

some tar balls may be as large as

pancakes, most are coin-sized. Tar balls are very

persistent in the marine environment and can travel 

hundreds of miles.

How Long Will Tar Balls

Remain Sticky?

Weathering processes eventually create a tar ball that

is hard and crusty on the outside and soft and gooey on

the inside, not unlike a toasted marshmallow. Turbulence

in the water or beach activity from people or animals 

may break open tar balls, exposing their softer, more 

fluid centers. 

Scientists have not been very successful at creating

weathered tar balls in the laboratory and measuring the

thickness of the crusty outer layer. Therefore, we don’t

know how much energy is needed to rupture a tar ball.

We do know that temperature has an important effect

on the stickiness of tar balls. As air and water 

temperatures increase, tar balls become more fluid and,

therefore, sticky — similar to an

asphalt road warmed by the 

summer sun. 

Another factor influencing

stickiness is the amount of 

particulates and sediments present

in the water or on the shoreline,

which can adhere to tar balls. The

more sand and debris attached to a

tar ball, the more difficult it is to

break the tar ball open. These 

factors make it extremely difficult to predict how long a

tar ball will remain sticky.

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National Oceanic and Atmospheric Administration

U.S. Department of Commerce

NOAA’s Oil Spill Response

Understanding Tar Balls
Are Tar Balls 

Hazardous to 

Your Health?

For most people, 

an occasional brief

contact with a small

amount of oil, while

not recommended,

will do no harm. 

However, some people

are especially sensitive

to chemicals, including

the hydrocarbons found in crude oil and petroleum 

products. They may have an allergic reaction or develop

rashes even from brief contact with oil. In general, we

recommend that contact with oil be avoided. 

If contact occurs, wash the area with soap and water,

baby oil, or a widely used, safe cleaning compound such

as the cleaning paste sold at auto parts stores. Avoid using

solvents, gasoline, kerosene, diesel fuel, or similar 

products on the skin. These products, when applied to

skin, present a greater health hazard than the smeared tar

ball itself.

Tar Ball Bits and Pieces

Beach Cleanup

There is no magic trick to making tar

balls disappear. Once tar balls hit the

beaches, they may be picked up by hand

or by beach-cleaning machinery. If the

impact is severe, the top layer of sand

containing the tar balls may be removed

and replaced with clean sand.

Are there more tar balls on beaches along the East Coast

than on the West Coast?

The number of tar balls found on the beach depends

on several factors: tanker traffic, wind patterns, sea 

currents, whether an oil spill occurred recently, and how

often the beach is cleaned. 

Obviously, some beaches may have more tar balls

than others, but to our knowledge, East Coast beaches are

not necessarily more polluted with tar balls than beaches

along the West Coast of the United States.

Can Dispersants Cause Tar Balls? 

No. Dispersants do the exact opposite- they break oil

up into tiny droplets, much smaller than the head of a pin,

which do not re-form or re-congeal into a visible mass 

of oil. 

Tar balls are weathered oil that has lost its lighter

components. Thus they are denser than fresh oil and

closer to the density of seawater. They still float, but in

estuarine (less dense) waters like Lakes Pontchartrain and

Borgne, they would float very low in the water and be

easily entrained by currents, as well as roll under or

around booms and barges. They are also widely scattered

and may not be noticeable at sea or floating, but may 

accumulate on shorelines.

Reporting

New tar balls appearing on a beach may indicate an

oil spill. If you notice unusual numbers of tar balls on the

beaches, call the U. S. Coast Guard any time at 

800-424-8802.

For additional information:

http://response.restoration.noaa.gov

http://response.restoration.noaa.gov/adios

NOAA’s Office of Response and

Restoration Emergency Response 

Division: 206-526-6317

Learn more about NOAA’s response to the BP oil spill at 

http://response.restoration.noaa.gov/deepwaterhorizon.

To learn more about NOAA, visit http://www.noaa.gov.

July 8, 2010