Geologic tilting, also known as tectonic tilting, occurs when the earth’s surface layers begin to tilt or slant irregularly. Geologists have studied the tilts of land, lakes and other bodies of water for hundreds of years and developed different theories to account for geologic tilting. Although there is disagreement about certain causes of tilting, it is generally accepted that tilting can occur as a result of faults (vertical and horizontal), angular unconformity and disturbances to the earth’s magnetic field.
A fault is a crack or fissure in the earth’s crust. Typically, faults cause movement in the earth’s surface, triggering phenomena like earthquakes. One kind of movement that faults trigger is vertical. For instance, when mountains or tall elevation in the earth’s surface crack, mountain blocks (the layers of the earth that form the mountain) move relative to the fault and displace the ground surface. The displacement of the surface may be mild or severe but typically causes tilting or irregularity in the surrounding land.
Horizontal cracks can occur underneath the earth’s surface or on the surface. The latter are known as surface fault ruptures. Horizontal faults, like vertical faults, disturb the formation of the earth’s layers and cause irregularities, including tilting. Surface fault ruptures can also cause tectonic subsidence, which is broad tilting of the valley floor. When valley floors tilt, lakes and reservoirs near the valley floor flood and tributary courses are disturbed.
Angular unconformity also causes geologic tilting. Angular unconformity occurs when parallel strata of sedimentary rocks are deposited on layers that are tilted, perhaps as a result of erosion. In short, new layers of sedimentary rocks are compressed on top of layers that are already deformed and tilting, thereby exacerbating tilting and causing further angular discordance.
Changes to Magnetic Field
Disturbances in the earth’s magnetic field also cause geologic tilting. Diverse phenomena have the potential to disturb the earth’s magnetic field, including passing comets or fluctuations in the sun’s magnetic field. No matter when magnetization is disturbed, the terrestrial axis of the earth is altered. This causes all kinds of geologic and climatological imbalances, including the tilting of lakes and layers of the earth’s surface because of subcrust migration. Essentially, the displacement of magnetic poles causes crustal displacements and other irregularities by dislocating (even over hundreds of years) the underlying strata of the earth.