The Osaka district is surrounded by the Hokusetsu Mountains, the Kongo-Ikoma Mountains, and the Izumi Mountain Range in northerly, easterly and sourtherly directions respectively. Hills are situated at the foot of the mountains, and plains spread over the lowlands reaching Osaka Bay.
Active faults bounded the mountins, and the hills and plains. The mountains are made of old strata and plutonic rocks of late Paleozoic and Mesozoic eras, while hills and plains are covered by new deposits of the late Cenozoic. The present geographical features have been built up with the motion of active faults which led the mountains higher and the plains lower, associated with huge earthquakes at intervals of about 1000 years.

• Geological map of Osaka district
• Active faults and earthquakes