Earth’s Interior Section1

Exploring Inside Earth Geologists have used two main types of evidence to learn about Earth’s interior: Direct evidence from rock samples Indirect evidence from seismic waves

Evidence From Rock Samples Rocks from inside the earth give clues about Earth’s structure Geologists find these rocks by drilling holes into the Earth The way the rocks are formed shows geologists the conditions inside the earth

Seismic Waves Seismic Waves: Vibrations that travel through Earth carrying the energy released during an earthquake. The speed of seismic waves and their paths reveal the structure of the earth. The information given from seismic waves has revealed the make up of the Earth’s interior layers.

Layers of Earth 3 Main Layers of the Earth Crust: Mantle: Core: These levels vary greatly in size, composition, temperature, and pressure.

Temperature and Pressure Temperature inside the earth increases 1 degree Celsius every 40 meters we travel down into the earth. Pressure results from a force pressing on an area. Pressure increases the further you go down in the earth due to the weight of the material in the layer above.

The Crust Crust is the layer of rock that forms Earth’s outer skin. It is a layer of solid rock that includes both dry land and the ocean floor. Crust is thickest under high mountains and thinnest beneath the ocean. Oceanic crust is mostly made up of a rock called Basalt. This is a dark rock with a fine texture. Continental crust (the crust that forms continents) consists mainly of granite. Granite is usually light in color and has a course texture.

The Mantle 40 Kilometers below the Earth’s surface, you will hit the mantle. The mantle is made up of very hot rocks that can be divided into 3 sections: Lithosphere: Rigid layer similar to the crust Asthenosphere: A softer layer, similar to tar or plastic. It is softer than the rest but still a solid. Lower Mantle: Solid material that extends all the way to Earth’s core.

The Core The Core is made mostly of the metals iron and nickel. It has 2 parts: The Outer Core: Molten metal that surrounds the inner core. This is a liquid. The Inner Core: A dense ball of solid metal. Earth’s metal core is the reason for the magnetic field surrounding Earth and the alignment and orbiting of the other planets.

Convection and the Mantle Section 2

Types of Heat Transfer There are 3 types of Heat Transfer 1. Radiation: The transfer of energy through space. Example: Sunlight, heat from a fire, heat from a flame. 2. Conduction: Heat transfer within a material or between materials that are touching. Example: A spoon that heats up while stirring a hot pot of soup. 3. Convection: Heat transferred by movement of liquids and gases.

Convection and Convection Currents It is caused by differences of temperature and density within a fluid. Density is the measure of how much mass there is in a volume of a substance. Convection Current: The flow of heat transfer within a fluid. Heating and cooling of the fluid, changes in the density, and the force of gravity combine to set convection currents in motion.

Convection Current: As a material heats (water, magma, etc Convection Current: As a material heats (water, magma, etc.) it rises, as it rises it cools, as it cools it sinks, as it sinks it heats, as it heats it rises. It is a cycle that continues. In Earth, heat from the core and the mantle itself cause convection currents in the mantle.

Pieces of the lithosphere (plates) float on the asthenosphere. Hot magma rises & cooler magma sinks creating convection currents (like boiling water)

Drifting Continents Section 3

Continental Drift Alfred Wegener hypothesized that all the continents were once joined together in a single landmass and have since drifted apart. That theory became known as Continental Drift. Wegener named the supercontinent before the continents began to drift Pangaea. Pangaea means “all lands” Wegener studied land features, fossils, and evidence of climate change to support his theory.

Continental drift – Pangaea = the super continent.

Evidence of continental drift – magnetic reversals in seafloor spreading. Oldest Rocks Youngest Rocks

Plate Tectonics Plate Tectonics: The formation, movement, and subduction of Earth’s Plates. When plates collide or slide apart, volcanoes & earthquakes occur. Most (90%) volcanoes & earthquakes occur in the Ring of Fire around the Pacific Ocean.

What happens when two plates collide? Basalt = high density Granite = low density What happens when two plates collide?

Mid- ocean Ridge An undersea mountain chain where new ocean floor is produced. A mid-ocean ridge is a Divergent Boundary Divergent Boundary: The place where two plates move apart On land, they are called Rift Valleys.

Convergent Boundary The place where two plates come together When two plates come together it is called a collision When continental crust collides with continental crust, they create mountain ranges. When oceanic crust collides with oceanic crust, one layer goes under the other layer. This is called a Subduction Zone. A subduction zone is also formed when Oceanic crust collides with continental crust. Oceanic crust is more dense than continental crust.

Divergent boundary Example: mid-ocean ridge (Mid-Atlantic ridge) Convergent boundary Example: Cascade mountains (west USA)

Transform Boundary A place where two plates slide past each other, moving in opposite directions. Earthquakes usually occur at transform boundaries No crust is created or destroyed at transform boundaries

Plate Boundaries Where in the world can we find examples of each boundary? What features would you expect at each boundary?