Mass Extinction Events There have been 5 major

Mass Extinction Events There have been 5 major mass extinction events in the history of Earth. - We are witnessing the start of the 6 th – This time it is caused by human activity!

History of Earth in born - 4. 54 billion years ago Earth surface hardens - 4 billion years ago Life emerges on the planet - 3. 8 billion years ago Hominid species differentiate from apes - 6 to 8 million years ago Homo Erectus stands up - 1. 7 million years ago Neanderthal Man appears - about 400, 000 years ago Homo Sapiens (us) appears in Africa - about 300, 000 years ago Homo Sapiens migrates to Southeast Asia and the Middle East about 100, 000 years ago Human "Civilization" begins - 10, 000 years ago The Industrial Revolution's devastating impact on the Global Climate becomes obvious - 100 years ago

List of the first five • Ordovician-Silurian – 70% of all species became extinct – 450 Million Years Ago • Late Devonian – 70% of all species became extinct – 375 million years ago • Permian-Triassic – 95% of all species became extinct – 150 Million Years Ago • Triassic-Jurassic – 75% of all species became extinct – 200 Million Years Ago • Cretaceous-Paleogene– 75% of all species became extinct– 66 Million Years Ago

Number 1 • Ordovician-Silurian – 70 to 85% of all species became extinct – 450 Million Years Ago – Probable Cause: Extensive volcanism initiated a rapid and short ice age. – Glaciation resulted in sea level fall and most life lived in the sea. – Oxygen levels in the sea plummeted. – Toxic metals in the sea floor dissolved in the sea water.

Number 2 • Late Devonian – 70% of all species became extinct – 375 million years ago – Most life was still in the sea, but land mass plants and insects had appeared – Most probable cause: Plate shifts, volcanism, and sea anoxia (lack of oxygen) associated with global cooling.

Number 3 • Permian-Triassic – 95% of all marine species and 70% of all terrestrial vertebrate species became extinct – 250 Million Years Ago – Possible causes: • Volcanism, sea anoxia, and sudden release of methane from the sea floor. • Major impact event from large asteroid

Number 4 • Triassic-Jurassic – 75% of all species became extinct – 200 Million Years Ago – Possible causes of associated intense global warming: • Volcanic activity • Asteroid impact

Number 5 • Cretaceous-Paleogene – 75% of all species (including almost all non-avian dinosaurs) became extinct– 66 Million Years Ago – Probable causes: • Volcanic activity • Asteroid impact

Number 6 • Holocene (Anthropocene) – Degree of extinction yet to be determined – Began about 10, 000 years ago when homo sapiens became “civilized” and is currently ongoing – The causes of 1 through 5 are understood with varying degrees of certainty. – The cause of 6 is the result of human activity; “Anthropogenic Global Warming”, and the associated Climate Change. – Humans have existed only for the last 200, 000 years or so and “Human Civilization” began on about 10, 000 years ago. – It is highly probable that the number of species that become extinct will be nearly total and humans almost certainly will not survive. – Dramatic mitigation activity by humans could disrupt the trend but when the atmospheric CO 2 concentration reaches 6 degrees C above preindustrial levels the extinction is virtually certain. We are nearing 2 degrees now and the trend continues upward.