Reading the Earth’s Timeline: Law of Superposition Quiz

If gravity pulls sediment down uniformly, then the resulting deposit will be flat; if this is a fundamental rule of geology, then the principle of original horizontality is true.

If the Grand Canyon is a sequence of stacked sedimentary layers, and if the law states the bottom is the oldest, then the bottom layers of the canyon are indeed significantly older than those at the rim.

If the intrusion cut through 1 and 2, it is younger than them; if it did not cut through Layer 3, then Layer 3 must have been deposited after the intrusion hardened; therefore, Layer 3 is the youngest.

If layers are visible, then we can see the order; if they aren't flipped, the oldest is at the bottom; if they are sedimentary, they formed in sequence; therefore, A, B, and C are necessary.

If we use the Latin-derived term for "layers" in a geological context, then we use the word strata (singular: stratum).

If a method determines if one thing is older than another without using numbers, then it is a comparison; if it is a comparison, then it is called relative dating.

If the leaf layer is below the shell layer, then the forest existed first; if the shells are on top, then the ocean covered the area later; therefore, the environment changed from forest to ocean.

If a fault breaks through rock layers, then the layers must have already existed for the break to happen; if the layers existed first, then the fault is the younger feature.

If molten rock forces its way into older, solid rock layers, then it is "intruding" into that space; if it cools and stays there, then the resulting feature is an intrusion.

If a rock layer is eroded away and new sediment is deposited on top, then there is a "missing" period of time in the sequence; if there is a gap in time, then it is termed an unconformity.

If new layers of sediment are deposited on top of existing ones, then the layer at the bottom must have been there first; if it was there first, then it is the oldest in the sequence.

If the trilobite is in a lower layer and the dinosaur is in a higher layer, and if lower layers are older, then the trilobite layer must have formed before the dinosaur layer.

If earthquakes tilt layers, then the order changes; if magma (intrusions) cuts through layers, then it alters the sequence; if erosion removes layers, then the record is broken; therefore, A, B, and C are disruptions.

If we look at the history of geology in the 17th century, then we find that Nicholas Steno formulated the principles of stratigraphy; therefore, he is the scientist credited with this law.

If relative dating compares layers to determine which is older or younger than another, then it only provides an order of events; if it only provides an order, then it does not provide a specific numerical age.

If particles are suspended in water or air, then gravity pulls them downward; if they are pulled downward to a flat surface, then they settle into horizontal sheets.

If younger material is deposited on top of older material, and if Layer A is the topmost layer in this sequence, then Layer A must be the most recently formed or youngest.

If "strata" refers to layers and "graphy" refers to writing or study, then the scientific discipline dedicated to analyzing these rock layers is stratigraphy.

If sedimentary rocks form from the gradual accumulation of particles in water or air, then they naturally settle into flat horizontal layers; if they form layers, then they are the primary subjects of the Law of Superposition.

If the Law of Superposition assumes layers are "undisturbed," and if tectonic activity shifts or flips those layers, then the original chronological order is lost; therefore, the law cannot be applied simply to disturbed layers.