The 80-foot whale, a full-grown female, apparently died of blunt-force trauma, Supervising State Park Ranger Michael Grant said.
Researchers suspect the whale hit a ship out in the ocean before washing ashore.
The carcass was first spotted Saturday morning at the southern end of Bean Hollow State Beach. A whale fetus was found about 30 to 40 feet away, Grant said.
He said that when he saw the whale on Sunday, he was amazed by its size.
"I was surprised by the enormity," he said.
Researchers are now trying to determine what to do with the carcass, Grant said.
The investigation is being led by the California Academy of Sciences and is in conjunction with the Marine Mammal Center and the University of California, Santa Cruz's Long Marine Lab.
