Why the Price of Oil Is Surging - in One Picture

The price of oil is still on the rise today (Tuesday). As of 12:35 p.m. GMT (7:35 a.m. EST) today, Brent traded at $56.38 a barrel, a nearly 3% gain from its previous value.

That puts Brent oil up 14% since last Friday (Jan. 30). And on that day, Brent surged 8% - its biggest one-day gain since 2009.

WTI crude traded this morning at $50.88, up roughly 2.6% since Monday night.

Oil prices are surging for one reason, and this picture says it all:

price of oil
Workers from the United Steelworkers (USW) union walk a picket line outside the Shell Oil Deer Park Refinery in Deer Park, Texas, on Feb. 1, 2015. Richard Carson-Reuters

You see, Tuesday's oil price rise comes on the third day of the biggest national oil workers' strike since 1980.

About 3,800 United Steelworkers (USW) union members walked off nine refineries Sunday. USW said it "had no choice." The union could not agree on new contracts offered by lead negotiator Royal Dutch Shell Plc. (NYSE ADR: RDS.A, RDS.B) on behalf of several major oil companies including Exxon Mobil Corp. (NYSE: XOM) and Chevron Corp. (NYSE: CVX). The contract would cover workers at 63 U.S. plants.

The strike threatens to disrupt as much as 64% of total U.S. fuel output.

"The problem is that oil companies are too greedy to make a positive change in the workplace," USW international vice president of administration Tom Conway said to TIME. "They continue to value production and profit over health and safety, workers, and the community."

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Shell has said it would like to continue talks.

"We remain committed to resolving our differences with USW at the negotiating table and hope to resume negotiations as early as possible," Shell said to Reuters.

In the meantime, oil companies have said they would call for replacement workers. That way, the strikes would not to cause a spike in gas prices.

But according to Bloomberg, more refineries may join in the protest.

For an in-depth look at the USW strike and its effect on oil prices in 2015, go here...