1) Conformable contact: This is a contact between two rock layers that are parallel to each other. This indicates that the two rock layers were deposited at the same time.

2) Unconformable contact: This is a contact between two rock layers that are not parallel to each other. This indicates that there was a period of erosion or non-deposition between the deposition of the two rock layers.

3) Fault contact: This is a contact between two rock layers that have been displaced by a fault. This indicates that there has been movement along the fault after the two rock layers were deposited.

4) Intrusive contact: This is a contact between an igneous rock and a pre-existing rock. This indicates that the igneous rock was intruded into the pre-existing rock after it had solidified.