Monday Time Scales –Human time frames versus geological time frames –Various time scales Human, biological, geological & astronomical

Time frames and amount of impact relating to various geologic phenomena

HDF – 1995 and HUDF

Relative age –Youngest or oldest Absolute age –Age in number of years (Numerical) Measuring Time

Relative Age Law of Superposition: younger on older Law of cross-cutting relationships Law of Original Horizontality Law of Faunal Succession

Superposition

Cross-cutting Relationships

Putting it together

Hutton’s Unconformity

Faunal Succession

Geologic Time scale Eras Cenozoic - “recent life” –age of Mammals <66 mya Mesozoic - “middle life” – age of Dinosaurs mya Paleozoic - “ancient life” –Age of Trilobites mya Precambrian – Proterzoic & Archean

Cenozoic Mesozoic Paleozoic Precambrian

Feathered dinosaurs

Coelacanth; ‘fossil’ fish Trilobite

Precambrian Fossil deposits

Absolute Age Involves ‘decay’ of atoms A constant process that occurs with atoms

A process involving the nucleus

A loss of 2 protons & 2 neutrons Converting a neutron to a proton

Absolute Age Clock starts when Parent atoms are “trapped” in rock at time of crystallization. Therefore must be Igneous rock. Volcanic rocks cool quickly thus are best. With time Daughter atoms form and are trapped. We count number of Parent atoms and Daughter atoms.

Age of Earth Oldest ocean crust 3.8 x 10 9 or 3.8 billion years old (Greenland) –Indicates plate tectonics at work Oldest Rocks: 4.28 x 10 9 years or 4.28 billion years old (Canada) –Indicates stable crust exists Oldest Mineral: 4.4 x 10 9 years or 4.4 billion years old (Australia) –Indicates oldest date of rocks Meteorites (and Earth) 4.56 x 10 9 years or 4.56 billion years