🌍 Continents & Oceans – Short Study Notes

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🪨 Rocks

🔥 Igneous Rock

• Formed when magma cools & solidifies
• Primary/original rocks

📌 Types

• Intrusive → solidifies inside Earth
• Extrusive → solidifies outside Earth

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🧱 Sedimentary Rock

• Formed by deposition of sediments (broken, transported, deposited)
• Found in layers (strata)

📌 Key Features

• Lithification → compaction process
• Fossils present → important for history

🧩 Types

• Mechanical → sandstone, limestone, shale
• Organic → chalk, limestone, coal
• Chemical → limestone, halite

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🔄 Metamorphic Rock

• Formed by recrystallisation & reorganisation
• From Igneous + Sedimentary rocks under pressure, volume & temperature

📌 Types

• Thermal → due to temperature change
• Dynamic → without chemical change

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🌋 Volcano Types

• Cinder Cone → simple volcanic cone
• Composite → most viscous lava
• Shield → low viscosity lava
• Caldera → most explosive, collapses inward

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🌍 Continents

🌐 Continental Drift Theory

• Proposed by Alfred Wegener (1912)
• Continents were once joined, later drifted apart

⚙️ Causes

• Tidal force & Polar fleeing force
• Convection currents (cells) in mantle

🔍 Evidences

• Jigsaw fit of continents
• Fossil deposits similarity
• Placer deposits match

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🌊 Oceans

🪸 Corals

• Marine organisms → called “Rainforest of Sea”
• Live in colonies

🤝 Symbiosis

• With Zooxanthellae algae
• Mutual benefit relationship

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🌡️ Favourable Conditions

• Saline water (not fresh water)
• Sunlight & clear water
• Temperature → 30–35°C

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🌏 Barrier Reef

• Great Barrier Reef (Australia) → largest coral reef

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⚠️ Coral Bleaching

• Occurs when water becomes too warm
• Corals expel algae (Zooxanthellae)
• Turns corals white & weak

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🧠 Memory Tricks

• “Ignite = Igneous” → formed by fire/magma
• “Sediments = Layers” → sedimentary rocks
• “Meta = Change” → metamorphic transformation
• “Wegener = Wander” → continents drift
• “Coral = Clear + Warm + Salty” → survival conditions