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geology test 2024
| Question | Answer |
|---|---|
| What is continental drift? | -theory that continents have been slowly moving over geological time. -Proposed by Alfred Wegener, suggests all continents once formed a supercontinent called Pangaea around 220 million years ago, which gradually broke apart. |
| What evidence supports the continental drift theory? | -the fit of coastlines (like South America and Africa), -fossil similarities across continents -rock and landform similarities (like glacier-created formations), |
| What are tectonic plates? | Large, rigid sections of Earth’s crust, including both continental and oceanic crust, that move slowly over the mantle. These plates interact at their boundaries, creating various geological formations and phenomena. |
| Define seafloor spreading. | The theory, proposed by US geologist Harry Hess, which explains that new oceanic crust forms along mid-ocean ridges. Rising magma pushes the crust apart, creating new crust as it cools. This movement is driven by convection currents in the mantle. |
| What is a mid-ocean ridge? | An underwater mountain range created by seafloor spreading at divergent boundaries. The Mid-Atlantic Ridge is an example, where new crust forms as magma rises and solidifies. |
| What is a rift zone? | An area where the lithosphere (Earth's rigid outer layer) is being pulled apart. As tectonic plates diverge, a rift valley or deep valley forms, such as in East Africa. |
| What causes convection currents in the mantle? | Heat from Earth’s core causes magma in the mantle to become less dense and rise. As it nears the crust, it cools, becomes denser, and sinks, creating circular currents. These currents drive tectonic plate movement. |
| What is the crust? | The outermost layer of the Earth, also known as the lithosphere, ranging from 7-50 km thick. It is divided into tectonic plates and includes continental crust (thicker) and oceanic crust (thinner). |
| Describe the mantle. | The layer beneath the crust, about 2800 km thick, with temperatures from 500 to 3000 degrees Celsius. The upper mantle has semi-liquid magma, which causes tectonic plates to move, earthquakes, and volcanoes. |
| What is the outer core and its significance? | The outer core is a liquid layer mainly composed of iron and nickel. It ranges from 4000 to 6000 degrees Celsius and generates Earth’s magnetic field. |
| What is the inner core? | The solid, dense center of Earth with temperatures close to 10,000 degrees Celsius. Despite the heat, it remains solid due to extreme pressure from the surrounding layers. |
| Define constructive boundaries. | Boundaries where plates move apart, forming new crust (e.g., at divergent boundaries like mid-ocean ridges). These are associated with seafloor spreading and new ocean floor formation. |
| Define destructive boundaries. | Boundaries where plates converge, and crust is destroyed as one plate subducts beneath another (e.g., at convergent boundaries). This can form mountains, volcanoes, and deep-sea trenches. |
| What are convergent boundaries? | Boundaries where tectonic plates move toward each other. Depending on the types of plates involved, they can create mountain ranges, volcanoes, and trenches through processes like subduction. |
| Describe ocean-to-continent convergence. | When an oceanic plate collides with a continental plate, the denser oceanic plate subducts below, forming mountains, volcanic activity, and sometimes an ocean trench along the boundary. |
| Describe continent-to-continent convergence. | When two continental plates collide, they have similar densities, so they push against each other, causing the crust to fold and form mountain ranges (e.g., the Himalayas). |
| What is ocean-to-ocean convergence? | When two oceanic plates collide, the older, denser plate subducts, creating a deep ocean trench and potentially a line of volcanic islands or an island arc. |
| Describe divergent boundaries. | Boundaries where plates move apart, often forming rift valleys on land and mid-ocean ridges in the ocean. This process helped break up Pangaea and continues to shape Earth’s surface. |
| Explain transform boundaries. | Boundaries where plates slide past each other horizontally, often causing earthquakes along fault lines, such as the San Andreas Fault in California. |
| What is an earthquake? | A sudden release of energy along fault lines or tectonic boundaries, where seismic waves cause ground shaking. It can occur at all types of boundaries, especially transform and convergent. |
| What are P-waves and S-waves? | Types of seismic waves produced by earthquakes. P-waves (primary waves) compress and travel fast, while S-waves (secondary waves) are slower and more destructive. |
| How are earthquakes measured? | Using seismographs to detect seismic waves. The Richter Scale measures wave amplitude, while the Moment Magnitude Scale is more accurate and considers movement and force. |
| How does GPS detect tectonic plate movement? | By tracking base station positions on Earth's surface, GPS satellites measure the movement and direction of tectonic plates |
| What is a tsunami? | A large, destructive wave usually triggered by undersea earthquakes, volcanic eruptions, or landslides. Japan is highly vulnerable due to its location near several plate boundaries. |
| What causes volcanoes? | A: Volcanoes form when magma rises through the crust due to tectonic activity. Eruptions can occur at convergent boundaries or hotspots (e.g., Hawaii). |
| Explain the formation of the Hawaiian Islands. | Formed by a hot spot beneath the Pacific Plate, where magma rises, creating islands over millions of years as the plate moves over the hot spot |
| Why does Australia have limited earthquakes and volcanoes? | Located in the center of a Plate, far from active boundaries, - seismic activity is minimal compared to regions near plate boundaries. |
| What are convection currents and their effect on plates? | Circular magma movements in the mantle, transferring heat and causing tectonic plates to shift. Heated magma rises, cools near the crust, and sinks, driving plate tectonics. |
| How do volcanic eruptions benefit soil? | Eruptions deposit lava, ash, and minerals that, when broken down, create fertile soils. This attracts farming communities to volcanic regions despite potential risks. |
| Calculating plate movement | speed= distance/time |
| what are the boundaries of island arcs like | The majority of island arcs are located on subduction boundaries between two plates with oceanic lithosphere. lithosphere consists rigid crust,uppermost mantle. formation stages are Subduction initiates and the slab begins to descend into the mantle. |
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