Sam: Tectonic forces press on rocks and cause them to move out of the way or deform. Rocks can deform quickly by cracking. This is called geological faulting.

Animation. Two arrows press on a cross-section of stratified rock. The arrows slowly compress then eventually spring back as then rock cracks down the middle.

Sam: Rocks can also deform slowly by folding. Folds are commonly formed when faults cause rock layers to move out of the way. A fault-bend fold happens when a fault cuts all the way through folded layers. The layers bend as they get pushed over the fault.

Animation. A cross section of stratified rock is split in two by a fault that goes all the way through the top layer. The top section of the rock is slowly pushed up over the fault and bends.

Sam: A fault-propagation fold happens when a fault doesn't cut all the way to the top of the folded layers. This forces the layers on top of the fold to make space for the rock. Moving along the fault underneath.

Animation. A cross section of stratified rock is split by a fault. The fault goes up halfway through the layers. The rock is slowly bent as it is pushed along the fault.

Sam: In Dinosaur Peak, since the faults don't cut all the way to the top, these are probably fault-propagation folds.

An eroded mountain is seen in the distance. Layers of rock are bent with some of them almost vertical.

Sam:Hi, my name is Sam Shekut. I'm a PhD candidate here at the University of British Columbia, where I study sedimentary geology. In my studies, I use the layers of the earth to reconstruct past environments.