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Earth's Evolution: From Formation to Present
Sep 10, 2024
History of Earth
Formation of the Solar System
4.5 billion years ago
: Solar system formed from a dense cloud of interstellar gas and dust.
Cloud collapsed into a swirling disc of matter.
Hydrogen fused into helium, leading to the birth of the Sun.
Formation of the Earth
Clumps of matter in the disc formed planets and moons.
Inner planets (like Earth) formed from rocky materials closer to the Sun.
Young Earth was volcanically active, releasing gases:
Hydrogen sulfide, methane, carbon dioxide.
Early Collisions and Atmosphere
Earth experienced violent collisions:
Thea
, a Mars-sized planet, collided with Earth, forming the Moon.
No oceans initially; water existed as gas.
3.8 billion years ago
: Earth cooled, water condensed, creating the first oceans.
Origin of Life
3.7 billion years ago
: Earliest forms of life appeared (microscopic organisms).
Nearly a billion years later, organisms evolved and changed the world.
Formation of Continents
First continents emerged from ancient oceans (called cratons).
Formation of the first supercontinent,
Valbara
.
Evolution of Oxygen Producers
2.4 billion years ago
: Cyanobacteria evolved to photosynthesize, producing oxygen.
Resulted in lower CO2 levels, leading to the first ice age.
Continental Movements and Supercontinents
Continents broke apart and reassembled into
Rodinia
(largest supercontinent).
Rodinia broke apart, leading to
Pannotia
.
Cambrian Explosion
(540-485 million years ago): Explosion of life, evolution of hard-bodied animals.
Mass Extinctions
440 million years ago
: First mass extinction (Ordovician-Silurian extinction).
First trees and land animals evolved between
420-350 million years ago
.
250 million years ago
: Last vast supercontinent,
Pangea
.
Experienced the greatest mass extinction (about 90% of species).
Dinosaurs and Evolution
240-230 million years ago
: First dinosaurs appeared and dominated for 150 million years.
Example: Argentinosaurus and T-Rex.
Pangea eventually broke apart, forming modern continents.
Chicxulub Impact Event
6 million years ago
: Asteroid impact near present-day Mexico.
Caused climate changes, leading to the extinction of dinosaurs.
Emergence of Mammals and Humans
6 million years ago
: Earliest known human species,
Sahelanthropus
.
4 million years ago
: Early humans began walking upright.
800,000 years ago
: Discovery of fire, leading to cooking and heat.
40,000 to 15,000 years ago
: Extinction of other human species (except
Homo sapiens
).
Agricultural Development
10,000 years ago
: Emergence of the first farmers, settling down after a nomadic lifestyle.
Industrial Revolution and Population Growth
250 years ago
: Industrial Revolution transformed societies.
Human population:
1804: 1 billion
1927: 2 billion
Rapid increase since the 1960s, now over 8 billion.
Current Threats
Climate change threatens existence of humans and other life forms.
Rising temperatures, sea levels, and declining biodiversity could lead to another mass extinction event.
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