Introduction to Geography

• Geography studies Earth's landscapes, people, places, and environments, aiming to understand its functions and human impacts.

Three Main Foci in Geography

• Earth's physical geography
• Earth's human geography
• Earth's environment geography

The Four Spheres of Earth

• Atmosphere: The layer of gases surrounding Earth, encompassing air, weather, and climate.
• Hydrosphere: All water on Earth, including oceans, rivers, lakes, glaciers, and groundwater.
• Lithosphere (Geosphere): The solid part of Earth, which includes rocks, soil, mountains, and the Earth's crust.
• Biosphere: Encompasses all living things, including plants, animals, and microorganisms.

Spheres Interactions

• Changes in one sphere affect the others: For example, a volcano (geosphere) erupting affects the atmosphere, hydrosphere, and biosphere.

Earth's Structure

• Crust: The outermost and thinnest layer of the Earth, it is solid, hard, rigid and where we live.
• Mantle: The thickest layer, made of hot, semi-solid/melted rock and consisting of convection currents.
• Outer Core: A liquid layer made of iron and nickel.
• Inner Core: A solid layer also made of iron and nickel.

Plate Tectonics

• Pacific Plate: Covers most of the Pacific Ocean, from the west coast of the Americas to east Asia and Australia.
• North American Plate: Covers North America and parts of the Atlantic Ocean, extending into Siberia.
• Eurasian Plate: Covers most of Europe and Asia (excluding India and the Arabian Peninsula) and extends into the Atlantic Ocean.
• African Plate: Covers the continent of Africa and extends into the Atlantic and Indian Oceans.
• South American Plate: Covers the continent of South America and extends into the Atlantic Ocean.
• Indo-Australian Plate: Covers India, Australia, and parts of the surrounding ocean.
• Antarctic Plate: Covers Antarctica and extends outward into the Southern Ocean.

Pangaea

• Pangaea was a supercontinent about 200 million years ago, comprising all of Earth's continents joined together.

Continental Drift Theory

• Proposed in 1912 by Alfred Wegener stating that continents were once connected and have since drifted apart.
• Initial skepticism arose because Wegener couldn't explain what force moved the continents.
• Later discoveries showed that plate tectonics cause continental movement.

Evidence for Continental Drift

• Continents fit together like a puzzle.
• Similar landforms exist on different continents.
• Fossils of the same species are found on different continents.
• Evidence of past climate differences on continents is present.

Plate Tectonics Mechanism

• Heat inside the Earth moves plates through convection cells where warm mantle rock rises, cools, and sinks.
• These movements shift the Earth's crust and confirm Wegener’s continental drift theory.

Convergent Boundaries (Colliding Plates)

• Plates move towards each other and if two continental plates collide, mountains are created.
• If an oceanic plate collides with a continental plate, the oceanic plate subducts, forming trenches, volcanoes, and potentially causing earthquakes or tsunamis.

Divergent Boundaries (Plates Moving Apart)

• Plates move away from each other, causing seafloor spreading and forming mid-ocean ridges in oceans.
• On land, rift valleys and volcanoes are created, and plates may split, forming new ones.

Transform Boundaries (Plates Sliding Past Each Other)

• Plates move horizontally past each other, creating fault lines, such as the San Andreas Fault.
• When plates get stuck, pressure builds, leading to earthquakes when they break free.

Volcanoes

• Volcanoes are openings in the Earth's crust where molten rock (magma), gases, and ash erupt.

Shield Volcanoes

• Plate boundary: Divergent or hotspots (thin crust).
• Shape: Flat and symmetrical.
• Gradient: Gentle slopes.
• Lava type: Runny lava, no ash, hot liquid rock.
• Explosiveness: Not explosive.
• Eruption Frequency: Frequent.

Composite/Stratovolcanoes

• Plate boundary: Convergent (subduction) (thin crust).
• Shape: Conical and symmetrical.
• Gradient: Steep slopes.
• Lava type: viscous lava, ash and dust.
• Explosiveness: Very explosive.
• Eruption Frequency: Long periods of time between.

Features of a Volcano

• Magma Chamber: A store of molten rock deep inside the Earth.
• Crust: The thin top layer of the Earth's surface.
• Main Vent: The main column through which magma rises from the mantle through the crust.
• Lava Flow: Molten rock flows down the side of the volcano.
• Crater: A funnel-shaped hollow at the top of a volcanic cone.
• Ash Cloud: A hot mass of steam, gas, and dust pumped into the atmosphere during an eruption.
• Mud Flow: A mixture of ash, mud, and water, which is extremely fast-moving and dangerous.
• Side Vent/Cone: Magma that is forced to the surface via another route when the main vent is blocked.

Earthquakes

• Earthquakes are the shaking and vibration of the Earth's crust caused by the movement of tectonic plates.

Seismic Waves

• Vibrations that travel through the Earth during earthquakes or explosions.

Types of Seismic Waves

• Primary (P-Waves): Fastest, travel through solids and liquids, move in a push-pull motion.
• Secondary (S-Waves): Slower, only travel through solids, move in a side-to-side motion, and only travel through solids.
• Surface Waves: Slowest but most destructive, travel along the Earth's surface, causing shaking.

Focus (Hypocenter)

• The exact point inside the Earth where an earthquake starts releasing energy and sending out seismic waves.

Epicenter

• The point on the Earth’s surface directly above the focus where and earthquake is usually felt the strongest.
• Seismograph: records ground movements cause by seismic waves as they move through the earth

Measuring Earthquakes

• Magnitude: Measurement of earthquake strength.
• Richter Scale: Measures earthquake magnitude based on energy released, with each whole number increase meaning 10× stronger shaking and 32× more energy released.
• Moment Magnitude Scale (Mw): More accurate, especially for large earthquakes and measures total energy released.

Tsunami

• A series of large, powerful ocean waves caused by sudden movements in the water that can flood and destroy coastal areas.

Causes of Tsunamis

• Underwater Earthquakes: Most common cause, from tectonic plates shifting and displacing water.
• Volcanic Eruptions: Explosive eruptions or collapsing volcanoes push water outward.
• Landslides: Large rock or ice masses fall into the sea, forcing waves.

Tsunami Characteristics

• In deep water, waves move fast (up to 500-800 km/h).
• Waves are small in deep water but grow massively near the shore.
• It isn’t a single wave but a series of waves.
• Can flood kilometers inland.

Rock Cycle

• Rock Cycle: The process of changing rocks over time.
• Erosion: Process of breaking down rocks into smaller pieces.
• Sediment: Small pieces of rock, such as mud and sand, which are a product of erosion.