Cretaceous-Paleogene (K-Pg) Boundary

The Cretaceous-Paleogene (K-Pg) boundary, formerly known as the Cretaceous-Tertiary (K-T) boundary, marks a significant event in Earth's history, the mass extinction of the dinosaurs and many other species. This event occurred approximately 66 million years ago and is characterized by a layer of sediment containing high levels of the element iridium, likely from an asteroid impact, as well as other geological and biological markers.

Causes of the K-Pg Event

There are several proposed causes for the K-Pg event, with the leading theory being the impact of a large asteroid or comet. The impact would have released massive amounts of energy, causing widespread fires, tsunamis, and a "nuclear winter" effect due to the dust and debris thrown into the atmosphere. This would have disrupted the global climate and led to the extinction of many species, including the non-avian dinosaurs.

Geological and Biological Impact

The K-Pg event had a profound impact on the Earth's ecosystems. It led to the extinction of about 75% of Earth's species, including the dinosaurs, marine reptiles, ammonites, and many other organisms. This allowed for the rise of mammals and eventually led to the diversification of life in the Cenozoic era.

Study Guide

What is the significance of the K-Pg boundary?
Discuss the leading theories for the causes of the K-Pg event.
Describe the geological and biological impact of the K-Pg event.
How did the K-Pg event pave the way for the rise of mammals?

◂Chemistry Worksheets and Study Guides High School. Atomic Structure - Set I

Worksheet/Answer key

Atomic Structure - Set I

Worksheet/Answer key

Atomic Structure - Set I

Worksheet/Answer key

Atomic Structure - Set I

The resources above cover the following skills:

Concepts of Physical Science (SB1, SB2, SB3, SB4)

The student demonstrates an understanding of the structure and properties of matter by describing atoms and their base components (i.e., protons, neutrons, electrons).

The student demonstrates an understanding of the interactions between matter and energy and the effects of these interactions on systems by recognizing that atoms emit and absorb electromagnetic radiation.

Concepts of Physical Science (SB1, SB2, SB3, SB4)

The student demonstrates an understanding of the structure and properties of matter by using the periodic table to describe atoms in terms of their base components (i.e., protons, neutrons, electrons).