Why us the San Bernadino and the Rocky heading in different directions?

Question

I went to a school field trip but my notes are getting me confused. Does anyone know why the Rocky mountain ranges are going north and south while the San Gabriel and San Bernadino mountain ranges are going east and west? I know it's because of their plates... but i don't know what is on what plate!!! I think i got the North and South part right. Anyway, feel free to correct me if i am wrong. Thanks!

Answer 1

The San Gabriels and the San Bernardinos are uplifted.

The Rockies are remnants of the North American and Pacific plates' contact millennia ago.

Answer 2

you've got to remember that here in Southern California, our state, well the southern part of it where we live (Los Angeles, San Bernardino, the desert communities, San Diego), is being split in two parts by the San Andreas Fault. So all the land mass east of the San Andreas Fault is on the North American Plate, while everything west of the San Andreas Fault is on the Pacific Plate. At the moment the North American plate is moving westward towards the ocean because of the Atlantic Rift valley which is pushing it away from the European and African continents. Now, since the Pacific Plate is an oceanic plate, it's heavier than the continental North American Plate, where both plates meet (the San Andreas fault) there's a whole lot of grinding and every now and then all that pushing causes a release of energy, those are the earthquakes we feel.

At the moment, the area around SoCal has a bulge protruding into the North American plate causing it to have a lot of stress, the Pacific Plate here in SoCal is in a north/northeast direction.