Lecture 2

Reflects the geologic processes involved in its formation

The most abundant material on Earth, appearing in a vast variety of forms Composed of a collection of minerals, which are either chemical compounds or single elements Minerals determine a rock’s chemical composition and physical properties

Igneous rocks Sedimentary rocks Metamorphic rocks

Formed from cooling and crystallization of magma

Formed by lithification (compaction and cementation) of sediments

Formed by heat, pressure and chemical changes to another rock

They help identify and correlate rock layers of the same age in different locations

Remains or traces of prehistoric life, preserved in sediment or sedimentary rocks Essential for interpreting the geologic past and reconstructing past environments Used as time indicators to correlate rock layers from different regions

The study of fossils blending geology and biology

Rapid burial: protects remains from scavengers and surface decay Hard parts: bones, teeth, shells, and woody stems are more likely to be preserved Soft parts: rarely preserved unless in special conditions

unaltered remains permineralization molds and casts carbonization and impressions amber trace fossils

Teeth, bones, shells, or frozen/mummified organisms

Mineral-rich groundwater fills pores in organic tissue

Molds: formed when an organism leaves a hollow imprint in sediment Cast: mold is filled with mineral matter, creating a replica

Pressure removes liquids/gases, leaving a thin carbon film

If the carbon film is lost, fine-grained sediment preserves surface details

Organisms trapped in tree resin are sealed off, protected from decay

Indirect evidence of life, such as tracks, burrows, coprolites, and gastroliths

Evolutionary history: fossil records document the appearance, diversification, and extinction of species, providing evidence for evolutionary processes Extinction events: key insights into mass extinctions Environmental change: fossils reflects shifts in climate, sea level, and ecosystems over geologic time Dating and correlation: fossils assist in relative dating and correlating rock layers across regions Index fossils are especially useful

The process of determining the age of something

determining the numerical age of rocks or minerals by measuring the decay of radioactive isotopes in a sample

number of protons

protons plus neutrons

Variants of the same element that have the same number of protons but different numbers of neutrons, giving them different mass numbers