we are learning about landslides in my classand ive looked in my book and i cannot find the definition of bedding planeis it the same as the failure plane?or do lanslides occur along the bedding plane?
Yes, you got it right as did Ed. As sediment accumulates on a ocean bottom (for example) over time different sediments are deposited. Since it is roughly flat, it forms a planar surface. The bedding planes are the boundary between each plane (bed) of deposited sediment and as Ed pointed out, there is often a plane of weakness due something weaker that settled in one plane versus the others.
Layers of sedimentary rocks are called beds. Say, if you drive past a highway road-cut and see layers of limestone, sandstone or shale- the bedding plane is parallel to the layers. The boundary between beds can be a weak point, that might fail and lead to a landslide but the orientation of the bedding plane is important, if the bedding plane slopes downhill, obviously there's a much better chance of a slide, than if the beds are horizontal, or if the beds slope up.
a failure plane is not necessarily a bedding plane, but the existence of a natural plane of weakness due to the way sediments accumulate (as beds) makes a bedding plane failure a more likely event than one cutting across existing natural weakness. Things tend to find the easiest route to failure, and the easiest route usually involves existing weaknesses. Sometimes, though, the strongest direction of force is not very close to the direction of bedding, so failure occurs in other ways.
