BANDON, Ore. -- Another series of earthquakes added to the geological mystery off the Oregon Coast on Monday.

Four sizable quakes rumbled off the coastline in a span of four hours Monday night.

The largest, a 4.1 earthquake located 115 miles west of Port Orford, occurred at 7:17 p.m.

Over the past several weeks, there have been hundreds of small quakes west of the coastal towns of Bandon and Port Orford. They have varied in magnitude from 3.0 to above 5.0.

Scientists have said they don't know exactly what the earthquakes mean, but they could be caused by molten rock rumbling away from the recognized faults off Oregon.

Monday night's earthquakes:

7:17 p.m., 115 miles west of Port Orford, 4.1 earthquake.

7:58 p.m., 92 miles west of Bandon, 4.0 earthquake.

9:35 p.m., 103 miles west of Bandon, 3.9 earthquake.

10:41 p.m., 107 miles west of Port Orford, 3.7 earthquake.

Related:

Report An Earthquake To USGS