Earth's Layers and Plate Tectonics

Earth's Layers

• The four main layers of Earth are the crust, mantle, outer core, and inner core.
• The outer core is responsible for creating Earth's magnetic field.
• The outer core is liquid, while the inner core is solid.
• The mantle is the thickest layer of the Earth.
• The crust is the thinnest layer of the Earth.
• The two types of crust found on Earth are oceanic and continental crust.

Plate Tectonics

• A tectonic plate is a section of Earth's crust and upper mantle (lithosphere) that moves as a unit.
• A geological event caused by plate movement is an earthquake.
• A convergent plate boundary is where two plates collide; one example of what happens when the oceanic plate meets a continental plate is that the denser oceanic plate subducts beneath the lighter continental plate, leading to the formation of a subduction zone, volcanoes, and mountain ranges.
• Evidence supporting plate movement includes the fit of continental coastlines and the matching of fossil distributions across different continents.
• Pangea was the supercontinent that existed millions of years ago.
• Seafloor spreading is the process where new oceanic crust forms at mid-ocean ridges and moves away from the ridge; it supports plate tectonic theory because it demonstrates how new crust is created and how plates diverge.
• Tectonic plates move due to convection currents in the mantle.

Earthquakes and Volcanoes

• Earthquakes occur when there is a sudden release of energy in the Earth's lithosphere, creating seismic waves, usually as a result of movement along faults.
• Most volcanoes are found at plate boundaries because that's where magma can easily reach the surface, either through subduction zones or mid-ocean ridges.
• A subduction volcano forms when one tectonic plate sinks beneath another; the melting of the subducting plate generates magma that rises to the surface, creating a volcano.
• A shield volcano is broad and gently sloping, formed by fluid lava flows, while a stratovolcano is steep-sided and conical, formed by layers of ash, lava, and rock.
• The Richter scale measures the magnitude of an earthquake.
• The focus of an earthquake is the point within Earth where the rupture occurs, while the epicenter is the point on the Earth's surface directly above the focus.
• An example of a major earthquake is the 2011 Tōhoku earthquake in Japan.

Rocks and the Rock Cycle

• Sedimentary rocks are formed from compacted sediments.
• Igneous rocks are formed from cooled magma or lava.
• Metamorphic rocks are formed when heat and pressure change existing rocks.
• The two types of igneous rocks are intrusive and extrusive.
• Lithification is the process that turns sediment into sedimentary rock
• A metamorphic rock can become an igneous rock by melting and subsequent cooling and solidification.
• Weathering and erosion break down rocks into smaller pieces, which are then transported and deposited as sediment, eventually forming sedimentary rocks.
• Fossils help scientists understand Earth's past by providing evidence of past life forms and environmental conditions, which tell a story of what the earth looked like at that time.
• Intrusive igneous rocks cool slowly inside the Earth, resulting in large crystals, while extrusive igneous rocks cool quickly on the Earth's surface, resulting in small or no crystals.
• A sedimentary rock can become a metamorphic rock through heat and pressure.

Earth's Systems

• The four Earth systems are the atmosphere, hydrosphere, geosphere, and biosphere.
• The hydrosphere includes all water on Earth.
• The geosphere interacts with the atmosphere through volcanic eruptions releasing gases, and weathering processes consuming atmospheric gases.
• The role of the biosphere is to include all living organisms on Earth and their interactions with the other Earth systems.
• Human activity impacts the hydrosphere through pollution and overuse of water resources.
• Deforestation affects the carbon cycle by reducing the amount of carbon dioxide absorbed by plants, leading to an increase in atmospheric carbon dioxide.

Tsunamis

• Tsunamis are most commonly caused by underwater earthquakes.
• The 2004 Indian Ocean tsunami is an example of a major tsunami event in history.
• Tsunamis become more destructive near the coast due to the decrease in water depth, which causes the wave to slow down and increase in height.
• Two warning signs of an approaching tsunami are a sudden rise or fall in sea level and a loud roar coming from the ocean.
• If a tsunami warning is issued, you should move to higher ground away from the coast.

Māori Narratives and Natural Features

• According to Māori tradition, Aotearoa (New Zealand) was formed when Māui fished up the North Island from the ocean.
• Te Ika-a-Māui represents the North Island of New Zealand in the Māori creation story.
• Te Waka-a-Māui represents the South Island of New Zealand in the Māori creation story.
• According to Māori tradition, there are many volcanoes in Tāmaki Makaurau (Auckland) because Turehu people were fighting and their fires caused the volcanoes to form.
• Māori narratives explain natural disasters as the result of actions or emotions of gods; for example, earthquakes are associated with Rūaumoko, the god of earthquakes, who is restless beneath the earth.

Additional Concepts

• Acid rain forms when pollutants such as sulfur dioxide and nitrogen oxides react with water in the atmosphere to form sulfuric and nitric acids.
• Scientific evidence supporting the Earth being round includes observations that different constellations are visible from different latitudes and ships disappear hull first over the horizon.
• Studying earthquakes and volcanoes can help predict future geological events by identifying patterns in seismic activity, monitoring volcanic activity, and assessing geological hazards in specific regions.