Earth Science Week 4
The idea that laws in science that "work" in our world today also "worked" in the past.
Law of superposition
Within the layers of undisturbed rock, the oldest layers are on the bottom and the youngest layers are on top.(Refers to relative not numerical dating)
Principle of horizontality
Layers of sedimentary rock are laid down horizontal and this implies that if we find a rock where the layers are not horizontal some geological event has happened since their formation.
principle of cross cutting relationships
Igneous intrusion or a fault which cuts across
What kind of layers form when two distinct layers of sedimentary rock meet?
Layers are conformable or an unconformity exists.
Layers were laid down uninterrupted by time
Exists when the bottom layer is eroded before the next layer is laid down.
3 categories that unconformities are put in?
Angular, Disconformity, noncomformity
What is correlation or matching of rock layers at different points based on? (3)
Stratigraphy (order of layers), fossils in the layers, and types of rocks in the layers.
Study of fossils?
The remains or traces of once living things preserved in a rock structure.
Index fossils represent?
Organisms that as a species had a relatively short existence on the geological time scale and are found in wide spread geographical places.
Atoms of the same substance with different numbers of neutrons
Nuclear radiation or radioactivity?
The particles or energy being released to create stability.
when the nucleus gives off radiation and becomes smaller.
In Nuclear decay, the specific time that an _______ nucleus will decay is not predictable but the amount of decay in a ______ of nuclei is predictable.
Half life? Is this linear?
The amount of time that it takes for 1/2 of sample of similar radioactive isotopes to decay. No it's exponential.
One of the first radiometric substances used for numeric dating.
Span of time sub divisions?
Eons, eras, periods, epochs.
4 eon names?
Phanerozoic, Hadean, Archean, and proterozoic
largest section of the time scale?
What life appeared in the Precambrian period first? It developed to?
One celled organisms sin nuclei (prokaryotes)
Multi celled organisms con distinct nuclei (eukaryotes)
Paleozoic Era= Age of____ (3)
Besides animals, what else began to develop?
Invertebrates. Fishes. Amphibians.
Most common invertebrate animal in the Paleozoic period?
Mesozoic era= Age of ____ or _____
Reptiles or Dinosaurs
When did Pangaea break?
During the mesozoic era
How did the Mesozoic era end?
Extinction of dinosaurs.
Cenozoic era= ___era or Age of the ____
Humans are considered ____