Origin of the Universe and Earth

Origin of the Universe and Solar System

• Solar Nebula Theory posits the solar system originated from a spinning cloud of dust.
• Big Bang Theory suggests the universe began from an enormous explosion approximately 13.8 billion years ago.

Earth's Unique Characteristics

• Earth is the only planet in the solar system known to support and sustain life.
• Formed about 4.5 billion years ago, with its initial state being molten material.

Earth's Atmosphere

• Early atmosphere lacked oxygen, composed of carbon dioxide, steam, ammonia, and methane from volcanic eruptions.
• Photosynthesis by early organisms converted carbon dioxide and water into food energy and oxygen.

Endosymbiosis Theory

• Proposed by Lynn Margulis, suggesting eukaryotic cells evolved from primitive prokaryotic cells merging with plant and animal cells in symbiosis.

Geologic Time Scale

• A framework for understanding Earth history, divided into eons, eras, periods, and epochs.
• Eons are the largest intervals, lasting hundreds of millions of years.
• Eras mark significant events in Earth's history and are subdivided into periods.
• Periods are further divided into epochs, corresponding to chronostratigraphic series.

Earth Subsystems

• Four main subsystems: Atmosphere, Geosphere, Hydrosphere, and Biosphere.

Atmosphere

• Comprises several layers:
  • Troposphere: Contains most weather events.
  • Stratosphere: Houses the ozone layer.
  • Mesosphere: Meteors burn up here.
  • Thermosphere: High-energy radiation absorption.
  • Exosphere: Outermost layer, the boundary of Earth’s gaseous envelop.

Geosphere

• The largest sphere, extending from the Earth’s surface to its core, composed of solid rocky layers.

Hydrosphere

• Encompasses all water on Earth including streams, lakes, glaciers, and underground water.

Biosphere

• Represents all living organisms on Earth.

Continental Drift

• Theory proposed by Alfred Wegener in 1912, explaining the movement of continental landmasses.
• Noted the coastline similarities between western Africa and eastern South America.
• Pangaea was the single supercontinent from which modern continents have drifted.

Evidence Supporting Continental Drift

• Apparent fit of continents.
• Correlation of rock formations and mountain ranges across continents.
• Paleoclimate data revealing historical climate conditions.

Plate Tectonics

• Earth's crust is divided into plates moving at speeds of 1 to 10 cm per year.
• Most seismic activity occurs at plate boundaries, impacting both oceanic and continental crust.

Earth's Internal Structure

• Crust: Thin outermost layer composed of two types—continental and oceanic.
• Mantle: Middle layer, extending nearly 2,900 km, comprises both a solid lithosphere and a semi-fluid asthenosphere.
• Core: Center of the Earth composed of an iron-nickel alloy; outer core is in liquid form while the inner core is solid.