Earth and Space Science: Plate Tectonics, Carbon Cycle, Climate, Stars

Plate Tectonics Evidence

Continental fit, fossil evidence, matching rock layers, paleoclimate indicators, seafloor spreading, and magnetic striping all show that Earth's plates move over time.

• Continental fit (matching coastlines)
• Fossil evidence across now-separated continents
• Matching rock layers and geological sequences
• Paleoclimate indicators (evidence of past climates)
• Seafloor spreading at mid-ocean ridges
• Magnetic striping preserved in oceanic crust

Plate Structures

Different plate boundaries produce characteristic structures and landforms:

• Convergent boundaries: Volcanic mountains form where subduction causes magma to rise (example: Japan).
• Continental collisions: Non-volcanic mountain ranges form when two continental plates collide (example: the Himalayas).
• Divergent boundaries: Rift valleys form where plates move apart.
• Subduction zones: Oceanic trenches form where one plate is forced under another.

Fossils and Magnetite

Fossils show that continents were once joined and share similar life forms from those periods. Magnetite and other magnetic minerals align with Earth's magnetic field when they form; this alignment records the latitude and direction continents faced when those rocks formed, providing evidence of past continental positions.

Photosynthesis

Word equation: Carbon dioxide + Water + Light → Glucose + Oxygen

Chemical equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Respiration

Word equation: Glucose + Oxygen → Carbon dioxide + Water + Energy

Chemical equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Carbon Cycle

Carbon moves through the atmosphere, plants, animals, soil, oceans, and fossil fuels via processes such as photosynthesis, respiration, decomposition, and long-term storage.

• Atmosphere: carbon dioxide (CO₂)
• Producers: photosynthesis captures CO₂ into organic matter
• Consumers and decomposers: transfer and return carbon via respiration and decomposition
• Oceans: dissolve and store carbon
• Fossil fuels and sediments: long-term carbon storage

Weather vs Climate

Weather refers to short-term atmospheric conditions (day-to-day changes). Climate is the long-term average of weather over 30 or more years.

Industrialization and Carbon

Industrialization increases atmospheric CO₂ and other greenhouse gases. Ways to reduce carbon emissions and increase storage include:

• Reforestation and afforestation
• Renewable energy sources (solar, wind, hydro)
• Carbon capture and storage (CCS) technologies
• Soil carbon storage practices (reduced tillage, avoiding biomass burning)

Climate Change Impacts

Climate change can lead to a range of impacts including:

• Flooding
• Droughts
• Heatwaves
• Food shortages
• Stronger storms
• Sea-level rise
• Climate-driven migration and refugees

Collision Hypothesis

The collision hypothesis explains how planets and other bodies in the early solar system formed through repeated high-energy collisions between smaller rocky objects called planetesimals. In the early solar system, a cloud of gas and dust surrounded the young Sun, and gravity caused this material to clump together. As these clumps collided, some broke apart while others merged, producing large amounts of debris such as dust, rock fragments, and molten material. Over time, gravity pulled this debris back together, allowing bodies to grow larger through accretion. Repeated collisions and re-accumulation eventually formed planets, moons, and asteroids, while leftover debris created impact craters that are still visible on the Moon and other planets today.

Star Formation

Star formation begins in a nebula, a cloud of gas and dust. Gravity pulls the material together, forming a protostar that becomes denser and hotter. When nuclear fusion starts, a main-sequence star is formed. Then it evolves: lower-mass stars expand into red giants, while massive stars become red supergiants. After a star runs out of nuclear fuel, massive stars can expand and explode as a supernova, leaving behind either a neutron star or, if the core is very massive, a black hole.