Earth's Surface

• • The Earth's surface is composed of the crust, which is the outermost layer.
• • The crust is divided into continental crust (thicker, less dense, mostly granite) and oceanic crust (thinner, denser, mostly basalt).
• • Continents: Large landmasses (e.g., Africa, Asia).
  • Oceans: Large bodies of saltwater (e.g., Pacific, Atlantic).
• • Landforms are natural physical features on the Earth's surface.
• • Types of Landforms:
  • Mountains:
  • Formation: Created by tectonic forces such as collision and subduction (e.g., the Himalayas).
  • Characteristics: High elevation, steep slopes.
• Landform

  • Valleys:
  • Formation: Often formed by river erosion or glacial activity (e.g., the Grand Canyon).
  • Characteristics: Low areas between mountains or hills, often with a river running through them.
• Landform

  Plains

  • Formation: Formed by sediment deposition over long periods (e.g., the Great Plains).
  • Characteristics: Broad, flat areas, usually at low elevations.
• Landform

  • Plateaus:
  • Formation: Raised areas with a flat top, formed by volcanic activity or uplift (e.g., the Colorado Plateau).
  • Characteristics: Elevated flat areas.
• Landform

  • Hills:
  • Formation: Formed by geological activity such as erosion or faulting.
  • Characteristics: Smaller and less steep than mountains.
• Landform

  • Deserts:
  • Formation: Areas with very little precipitation, can be hot or cold (e.g., the Sahara Desert).
  • Characteristics: Sparse vegetation, extreme temperatures.
• Weathering:

  • Definition: The breakdown of rocks into smaller pieces by physical, chemical, or biological means.
• • Physical Weathering: Breakdown by physical forces (e.g., freeze-thaw cycles).
  • Chemical Weathering: Breakdown by chemical reactions (e.g., acid rain).
  • Biological Weathering: Breakdown by living organisms (e.g., plant roots).
• Erosion:

  • Definition: The movement of weathered material from one place to another by wind, water, ice, or gravity.
• • Water Erosion: Rivers and streams can carve valleys and transport sediments.
  • Wind Erosion: Wind can transport sand and create dunes.
  • Ice Erosion: Glaciers can carve out valleys and transport large boulders.
  • Gravity: Can cause landslides and rockfalls.
• Deposition:

  • Definition: The laying down of sediment carried by wind, water, or ice.
• • River Deposits: Form deltas and alluvial fans.
  • Wind Deposits: Form sand dunes.
  • Glacial Deposits: Leave behind moraines and drumlins.
• Soil Formation

  Definition:

  • Soil is the upper layer of the Earth where plants grow, composed of organic matter, minerals, gases, liquids, and organisms.
• • Weathering: Breaks down rocks into smaller particles.
• • Organic Matter: Decomposition of plants and animals adds nutrients.
• • Time: Soil formation is a slow process taking thousands of years.
• Soil Horizons:

  • O Horizon: Organic matter such as leaves and decomposed material.
  • A Horizon (Topsoil): Rich in organic material and minerals, vital for plant growth.
  • B Horizon (Subsoil): Contains minerals leached from the A Horizon.
  • C Horizon: Composed of partially weathered parent material.
  • R Horizon: Unweathered bedrock.
• Urbanization:

  • Building cities and infrastructure changes the landscape and disrupts natural processes.
• Deforestation:

  • Clearing forests for agriculture or development leads to increased erosion and loss of biodiversity.
• Agriculture:

  • Farming practices can lead to soil degradation and erosion if not managed sustainably.
• Mining:

  • Extracting minerals from the Earth can create large holes and disrupt ecosystems.
• Continental Drift Theory states that the continents have moved and are still moving today. In 1912 Alfred Wegener introduced this theory, but he did not fully understand what caused the plates to move.
• 250 millions years ago the Earth's seven continents were all grouped together into a supercontinent called Pangea.
• huge supercontinent was surrounded by one gigantic ocean called Panthalassa.
• Laurasia was made of the present day continents of North America (Greenland), Europe, and Asia.
• Gondwanaland was made of the present day continents of Antarctica, Australia, South America. The subcontinent of India was also part 
• The Triple Junction was formed because of a three-way split in the crust allowing massive lava flows. The split was caused by an upwelling of magma that broke the crust in three directions and poured out lava over hundreds of square miles of Africa and South America.
• The mid-ocean ridges are the longest continually running mountain range in the world. These ridges are connected and are about 40,000 miles long
• the Mid-Atlantic ridge , is spreading apart making the Atlantic Ocean wider. 
• boundary in which an oceanic plate is driven down and destroyed by a continental plate is called a subduction zone
• This Pacific Ocean region has more earthquakes and volcanic activity than any other area of the world. Because of all the volcanoes this region has been given the nickname of "The Ring of Fire" .
• When the less dense, lighter continental plate overrides the oceanic plate a subduction zone forms. Because the oceanic plate is bent and driven down, a deep trench forms at this collison point. These trenches are the lowest points on the Earth's crust
• There are two major regions of earthquake activity. One is the circum-Pacific belt which encircles the Pacific Ocean, and the other is the Alpide belt which slices through Europe and Asia.
• the layers will move along a crack in the Earth's crust called a fault or the release of energy will cause a new faultline to be produced.
• When an earthquake occurs an area of the crust will move very suddenly and with a great release of energy. The point of the actual rock rupture is called the focus, usually found far beneath the surface
• The point directly above the focus on the surface of the Earth is called the epicenter.