Around 10:15 a.m., CHP officers responded to a crash that was blocking northbound U.S. Highway 101 just north of Wilfred Avenue, south of Santa Rosa.
They arrived to find a Dodge Ram truck that had been hit by a Volkswagen Jetta, CHP officials said.
The crash was cleared from the roadway, and the Dodge driver was able to exit the freeway safely.
A CHP officer on a motorcycle drove ahead to the Santa Rosa Avenue off-ramp to help the Jetta exit as well.
However, the driver of the Jetta made an abrupt turn to the right while trying to exit and struck the officer, according to the CHP.
The officer was ejected from the bike and suffered minor injuries.
The driver of the Jetta was identified as Juan Carlos Avendan Ortiz, 23, of Rohnert Park. He was found to be unlicensed, had two prior convictions for driving without a license, and was on probation, according to the CHP.
Traffic was blocked for about 30 minutes on the freeway after the accidents, officials said.