Earth Sciences 240A Lecture 2

Part A: The Universe, Time and Philosophy

Course Content Introduction

Internal energy processes

Plate tectonics

Earthquakes

Volcanoes

External processes

Asteroid and comet impacts

Sun energy variations (Climate change)

Processes that disrupt life

Natural Evolution vs. Human Influence

Population growth influence

In the beginning……

Age of Universe (revisited)

Hubble’s Law: v=HoD, where v=velocity; Ho=Hubble const.; D= distance

Cosmological factor (λ)

Dark matter; Expansion acceleration

Accept 15-20 bya; Probably at least 20 bya

Origin of Heavy Elements

Initial massive stars; Iron (Fe) in core

Supernova; Elements heavier than Fe generated and spread

“Any system rich in heavy elements must be composed of products of supernovae”

Impacts

Late Heavy Bombardment (LHB); From 4 to ~3.8 bya

One of most violent events in Solar System history

Several 5000 km diameter

~40 >1000 km diameter

>22,000 >20 km diameter

Probably affected global environment every ~100 years

Early oceans vaporized periodically

Fragile carbon molecules destroyed

Crater size/Impactor size

Earth: 1 m meteoroid = 15 to 20 m crater

Earth’s Moon: 1 m meteoroid = ~50 m crater

Life

Immediately at end of LHB

~3.8 bya; very short ‘window’

Earliest fossils 3.5 bya

Role of comets/carbonaceous chondrites

Probably supplied both water and organic molecules

Next Lecture: Age Dating

Section 001 website: www.instruct.uwo.ca/earth-sci/240a