Earth Science: Layers and Natural Disasters

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Questions and Answers

What layer of the Earth is composed of solid rock and serves as the surface layer?

Core

Lithosphere

Crust (correct)

Mantle

Which of the following statements about the thickness of the Earth's crust is correct?

Oceanic crust is thicker than continental crust.

Continental crust is thicker than oceanic crust. (correct)

Oceanic crust could be as thick as 60km.

The crust is the same thickness everywhere on Earth.

What is the Moho boundary?

The separation between oceanic and continental crust.

The transition between the outer core and the mantle.

The boundary between the crust and the asthenosphere.

The boundary between the mantle and the crust. (correct)

What primarily causes the movement of the continents?

Convection currents in the mantle. Signup and view all the answers

What is the asthenosphere?

A liquid layer of the upper mantle that flows. Signup and view all the answers

What shapes do hardened lava forms typically have?

Steep and conical Signup and view all the answers

What are lahars primarily caused by?

Mixing of pyroclastic flows with water Signup and view all the answers

Which of the following events can cause a tsunami?

All of the above Signup and view all the answers

How does the speed and height of tsunami waves change near the coastline?

They become higher and slower Signup and view all the answers

What is a primary characteristic of pyroclastic flows?

They are composed of clouds of gases and ash Signup and view all the answers

What causes the inner core of the Earth to remain solid despite extremely high temperatures?

High pressure from the weight of Earth Signup and view all the answers

Which type of boundary is characterized by plates moving toward one another?

Convergent boundary Signup and view all the answers

What is the primary reason for the creation of new crust at divergent boundaries?

Rising molten rock from the mantle Signup and view all the answers

Which layer of the Earth is both the thickest and hottest?

Inner core Signup and view all the answers

What geological features are typically formed at convergent boundaries where oceanic plates collide?

Ocean trenches Signup and view all the answers

Which property of the asthenosphere allows lithospheric plates to float and drift?

Low viscosity Signup and view all the answers

Which of the following is NOT a feature associated with divergent boundaries?

Subduction zones Signup and view all the answers

Which process is responsible for the movement of plates in plate tectonics?

Convection currents in the mantle Signup and view all the answers

What is the primary composition of the Earth's inner core?

Iron and nickel Signup and view all the answers

Which geological process can lead to the formation of high mountains?

Subduction Signup and view all the answers

How does the density of oceanic crust compare to that of continental crust?

Oceanic crust is more dense Signup and view all the answers

What is the primary reason for the occurrence of earthquakes along transform fault boundaries?

Tectonic plate grinding past each other Signup and view all the answers

What was the name of the supercontinent that existed around 200 million years ago?

Pangaea Signup and view all the answers

What geological feature is primarily associated with earthquakes occurring?

Fault lines Signup and view all the answers

What term describes the point on the Earth's surface directly above where an earthquake originates?

Epicenter Signup and view all the answers

Which type of seismic wave is the fastest and is recorded first on a seismograph?

P wave Signup and view all the answers

What is the primary reason for the formation of magma within the Earth?

Pressure from above rocks Signup and view all the answers

What type of volcano is characterized by gentle slopes and is primarily composed of basalt?

Shield volcano Signup and view all the answers

What does the Richter Scale measure?

Magnitude of earthquakes Signup and view all the answers

Which of the following is NOT a type of volcanic eruption?

Hydrothermal explosion Signup and view all the answers

What is a secondary wave characterized by?

Up and down movement and cannot pass through liquids Signup and view all the answers

Aftershocks are typically caused by what phenomenon?

Sudden release of pressure from the main earthquake Signup and view all the answers

What drives the movement of magma towards the Earth's surface?

Less density compared to surrounding rocks Signup and view all the answers

Which of the following terms refers to a volcano that has not erupted in human history?

Extinct volcano Signup and view all the answers

What causes the trembling on the Earth's surface during an earthquake?

Release of energy from the focus Signup and view all the answers

Which type of volcanic rock forms when lava cools rapidly?

Igneous rock Signup and view all the answers

What geological phenomenon can lead to the creation of volcanic islands like those in Hawaii?

Hotspots in the mantle Signup and view all the answers

Study Notes

Earth's Layers

Crust: Solid rock, outermost layer, broken into plates (both major and minor). Oceanic crust is thinner (5 km) than continental crust (60 km). Boundary with the mantle is the Moho.
Mantle: Much thicker than the crust (2800 km), contains convection currents (heat circulation). The outer 200 km of the mantle is close to its melting point due to heat from the core, creating the liquid asthenosphere. Rock in the mantle flows, causing plate movement.
Core: Center of Earth, thickest and hottest layer (3470 km). Solid inner core and liquid outer core, primarily composed of iron and nickel. Outer core generates Earth's magnetic field. High pressure maintains inner core's solid state despite high temperature.

Plate Tectonics

Theory: Explains earthquake, volcano, and mountain formation. Continents are in continual motion due to stress at the surface from internal pressures.
Plate Boundaries: Where tectonic plates meet. Active regions for volcanoes and earthquakes.
- Divergent: Plates move apart, creating new crust (e.g., mid-ocean ridges, rift valleys).
- Convergent: Plates collide, leading to subduction (one plate moving under another), volcanic activity, and mountain ranges. (Oceanic-continental, Oceanic-oceanic, and Continental-continental).
- Transform: Plates slide past each other, creating friction and earthquakes (e.g., San Andreas Fault).

Key Properties of Earth's Layers

Layer	Thickness (km)	Density (g/cm³)	Temperature (°C)	State of Matter	Chemical Composition
Crust	5-70	2.7-3.0	~0-1,000	Solid	Silicates
Mantle	~2,900	3.3-5.7	~1,000-3,700	Solid (flows slowly)	Silicates rich in Fe, Mg
Outer Core	~2,300	9.9-12.2	~4,000-6,000	Liquid	Mostly iron (Fe) and nickel (Ni)
Inner Core	~1,220	~12.8-13.1	~5,000-7,000	Solid	Mostly iron (Fe) and nickel (Ni)

Continental Drift

Pangaea: Ancient supercontinent, one large ocean.
Evidence for plate movement and continental drift: Jigsaw fit of continents, similar rocks and fossils across continents, glacial evidence in locations where glaciers would not be expected today, and fossil records.

Earthquakes

Causes: Sudden movement along fault lines (fractures in Earth's crust) from sudden release of stress. Occur primarily at plate boundaries.
Measuring Earthquakes: Seismometers are used to detect and record earthquake vibrations. Richter and Shindo scales describe earthquake magnitude.
Seismic Waves: P-waves (primary) are faster, compressional, and travel through solids, liquids, and gases; S-waves (secondary) are slower, move side-to-side, and cannot travel through liquids or gases.
Focus & Epicenter: Focus = point of initial movement; Epicenter = point on surface directly above focus.
Aftershocks: Smaller earthquakes after a main earthquake caused by adjustments in the fault lines.

Volcanoes

Formation: Divergent and convergent boundaries, and hotspots.
Magma vs. Lava: Magma is molten rock below the surface, lava is molten rock released above the surface.
Types of Eruptions: Different types of eruptions exist, with some violent and explosive, while others are more gentle and slow-flowing.
Types of Volcanic Rocks/Materials: Volcanic dust, ash, cinders, igneous rocks (basalt, pumice).
Cones/Crater/Hotspots: Layers of cooled lava accumulate to form cones. Hotspots are areas in the mantle where magma is hotter, which rises. Volcanoes erupt as material is released from an elevated magma chamber.
Types of Volcanoes: Active, dormant, and extinct volcanoes. Different subtypes (shield, cinder cone, composite).
Pyroclastic Flows & Lahars: Fast-moving clouds of hot volcanic gases, ashes, and volcanic bombs. Lahars = mixed flows of ash and water from a volcano.

Tsunamis

Causes: Often from earthquakes but can also be from volcanoes or landslides.
Movement: Higher waves near the shore when the water is shallow; Lower, faster speed in deep oceans.
Impact: Massive destructive force on coastlines.

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Description

Test your knowledge on the Earth's layers, including the crust and asthenosphere, as well as natural disasters such as tsunamis, lahars, and pyroclastic flows. This quiz covers fundamental concepts in geology and earth science, providing a comprehensive overview of the Earth's structure and dynamics.