Our changing earth

 https://www.youtube.com/watch?v=vxmoxDznXe4

LITHOSPHERIC PLATES

Notes: Lithospheric Plates and Major Landforms

🌍 Lithospheric Plates

• The lithosphere is the solid outer layer of the Earth.

• It consists of the crust and the uppermost part of the mantle. 

• It is broken into pieces called Lithospheric Plates.

• These plates move very slowly due to the movement of molten magma inside the Earth.

• Magma moves in a circular manner, causing the plates to shift.

• The movement of these plates leads to changes on the Earth's surface.

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🌋 Types of Forces Acting on the Earth

1. Endogenic Forces

• These are internal forces that act inside the Earth.

• They can cause:

  • Sudden movements – like earthquakes and volcanoes.

  • Slow movements – like the formation of mountains and continents.(Diastrophic)

• Sudden movements often cause mass destruction.

https://www.youtube.com/watch?v=QLhKCr_qTJU

2. Exogenic Forces

• These are external forces that act on the surface of the Earth.

• Examples: weathering, erosion, wind, water, and ice.

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🌋 Volcano

• A volcano is a vent or opening in the Earth’s crust.

• Molten material (lava) erupts suddenly from this vent.

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🌎 Earthquake

• An earthquake is a sudden shaking or movement of the Earth's surface. It happens when the lithospheric plates (large pieces of Earth's crust) move. This movement causes vibrations that spread through the Earth in all directions.

Key Terms:

• Focus: The place inside the crust where the earthquake starts.

• Epicentre: The place on the surface directly above the focus.

  • The greatest damage happens near the epicentre.

  • Vibrations move outward in waves from this point.

Local Signs of Earthquake:

• Unusual animal behaviour, like:

• Agitated fish in ponds

• Snakes coming out of holes

• Changes in Water Levels or Flow

• Strange Animal Behavior

• Three Types of Earthquake Waves

1. P-Waves (Primary Waves)

• Fastest and first to arrive.

• Travel through solids, liquids, and gases.

• Move in a push-and-pull (back and forth) motion.

• Cause mild shaking.

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2. S-Waves (Secondary Waves)

• Slower than P-waves, arrive second.

• Travel only through solids, not through liquids.

• Move the ground side to side or up and down.

• Cause more shaking than P-waves.

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3. L Waves or Surface Waves

• Travel along the surface of the Earth.

• Arrive last but are the most damaging.

• Cause rolling or wave-like motion.

• Responsible for the destruction during earthquakes.

🔴 Think: Like ocean waves moving across land.

https://www.youtube.com/watch?v=17kBVfGjI8c&t=19s

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🏔️ Major Landforms

Landforms are shaped by the continuous process of weathering and erosion.

1. Weathering

• The breaking up of rocks on the Earth’s surface.

• It happens because of wind, water, heat, cold, or trees.

2. Erosion

• Erosion is the process of carrying away the broken pieces of rocks and soil.
  It is done by water, wind, or ice.

• The eroded material is carried and deposited elsewhere.

• This leads to the formation of different landforms.

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🏞️ Work of a River

1. Waterfall:

   • Formed when the river tumbles from a height over hard rocks.

2. Meander:

   • Large bends formed when a river twists and turns in plains.

3. Ox-bow Lake:

   • A cut-off meander loop that separates from the main river.

4. Flood Plain:

   • Flat, fertile land formed by deposits of fine soil (sediments) during floods.

5. Levees:

• Raised river banks formed by sediment deposits.

• A levee is also a raised bank built along the sides of a river to stop water from overflowing during floods.

1. Delta:

• Triangular landform at the river’s mouth, formed by deposited sediments.

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🌊 Work of Sea Waves

1. Sea Caves:

   • Hollow caves formed on rocks due to wave erosion.

2. Sea Arches:

   • Formed when sea caves grow larger and only the roof remains.

3. Stacks:

   • After the roof of a sea arch collapses, only rock pillars (walls) are left.

4. Sea Cliff:

• A steep, vertical rocky coast formed by strong wave erosion.

https://www.youtube.com/watch?v=8a3r-cG8Wic

Oxbow

Levee

Work of Ice

A glacier is a large, slow-moving mass of ice and snow.

It forms in very cold regions where snow collects year after year and gets pressed into ice.

Glaciers move slowly downhill due to gravity and their own weight.

They are often called "rivers of ice."

As glaciers move, they erode the land beneath them (scrape and cut the land).

They leave behind deep basins or hollows in the ground.

When the glacier melts, water fills these hollows, creating glacial lakes.

These lakes are often clear, cold, and surrounded by mountains.

As glaciers move, they pick up and carry rocks and soil.

When the glacier melts, this material is left behind.

These deposits are called moraines.

Moraines can form ridges or hills and are made up of mixed rocks and dirt.

Work of Wind

Wind: In the desert, an active agent of erosion and deposition is wind.

Mushroom Rocks: In deserts, rocks can be shaped like a mushroom, commonly called mushroom rocks.

Sand Dunes: When the wind blows, it lifts and transports sand from one place to another. When it stops blowing, the sand falls and gets deposited in low hill-like structures. These are called sand dunes.

Loess: When the grains of sand are very fine and light, the wind can carry them over very long distances. When such sand is deposited in large areas, it is called loess.

How Are Beaches Formed?

• Beaches are formed by the action of waves in seas or oceans.

• When waves hit the shore, they bring sand, pebbles, and shells from the sea and deposit them along the coast.

• Over time, this deposited material builds up to form a beach.

• Beaches can be made of sand, small stones, or gravel, depending on the area.