By Jose Hernandez & Roxana Arcos Phys. Geo. Mon/Wed 8AM

Basic Principles: Laws of Nature don’t change with time Includes Chemical and Physical laws Physical : Gravity Chemical : Combo of Hydrogen and Oxygen

Sediment layers first deposited in horizontal position - Flat layers undisturbed and in original position - Deposition leads to layers bending or folding

Interruptions in rock forming processes Reflect gap in geologic time What happens?! 1) deposition of sediment stops 2) erosion removed previously formed rocks 3) deposition resumes

Angular Unconformity Folding or tilting during interruption 1) older strata deposited in a horizontal position 2) Tilting/folding of sediment 3) Erosion of altered sediment 4) Deposition of young sedimentary rock on top

Nonconformities - Eroded surface separates older metamorphic or intrusive igneous rocks from younger sedimentary rocks. Disconformities Two sedimentary rock layers that are separated by a parallel erosion surface Animations

When determining an age of a rock we do not measure in years but in events, such as the existence of fossils to the age of the physical events. To determine the RELATIVE age of a rock Geologist use four principles

Oldest rock bed found in bottom layer Youngest rock bed at the top

Used for: 1) Finding natural resources 2) Standard for the geologic column Fossil remains occur in chronological order Oldest group have soft bodied organisms Intermediate groups have marine invertebrates, simple marine, amphibians, dinosaurs Youngest group have reptiles, birds, mammals.

This principle states igneous intrusions and faults are younger than the rock they cut. Igneous Intrusion

This principle states that a fragment of a rock incorporated or included is older than the host rock. Host rock Older Rock fragments

What in the is a geologic column?? A geologic column is a time scale constructed by age correlations using fossils to create a geologic time scale that serves as a calendar for the history of Earth. The geologic time scale is organized by Eons | Eras | Periods

Phanerozoic EONS Precambrian (Haden, Archean, Proterozoic) ERAS Cenozoic Mesozoic Paleozoic Neoproterozoic Mesoproterozic Paleoproterozoic Neoarchean Mesoarchean Paleoarchean Eoarchean PERIODS Millions in years Quaternary (present) Tertiary Cretaceous Jurassic Triassic Permian Pennsylvanian Mississippian Devonian Silurian Ordovician Cambrian

Geologic Column : Faunal succession style Phanerozoic Precambrian

Radioactive dating is a method used to measure geologic time in terms of a specific number rather than using the four principles of Relative Dating. Radioactive dating is measured by calculating the decay from an radioactive isotopes such as- Potassium 40 ( 1.25 b. HL), Carbon (5,730 HL), and so on. Time is then measured by the amount of the parent isotope left.

Radioactive Decay follows a rule known as half-life and all parent atoms decay to form daughter atoms. Half-life is different for each atom but for example the half-life of Potassium-Argon 40 is 1.25 billion years. While parent isotope decreases, daughter isotope increases over time. Potassium- Argon Billion

Place these geologic events in chronological order

B, C, E, D, A