Earth’s Interior, Seismic Waves and Tsunami | Grade 8 Science DepEd MELC Quarter 2 Module 2

Summary

This video script explains how earthquakes generate seismic waves that help scientists study the Earth's interior. It differentiates between body waves (P and S waves) and surface waves (Love and Rayleigh waves), highlighting their speeds and impacts. The script also discusses how underwater faults can cause tsunamis, emphasizing the need for caution near the sea during earthquakes. It concludes by noting that seismic waves reveal the Earth's layered structure.

Takeaways

• 🌏 Earthquakes assist scientists in understanding the Earth's interior by generating seismic waves.
• 📊 Seismic waves are detected and recorded by seismographs, which produce seismograms.
• 🌀 There are two main types of seismic waves: body waves (P and S waves) and surface waves (Love and Rayleigh waves).
• 🏃‍♂️ P waves are the fastest and can travel through any material, while S waves are slower and can only travel through solids.
• 🌊 Surface waves cause most of the damage during earthquakes and travel slower than body waves.
• 📉 Seismic waves provide information about the Earth's layers, such as the transition from solid to liquid outer core.
• 🌊 Tsunamis are caused by underwater faults that move vertically, displacing a large volume of water.
• 💨 Tsunamis travel fast in the open ocean but slow down and increase in height as they approach the shore.
• 🏞️ Not all underwater fault movements result in tsunamis; only vertical movements can cause them.
• ⚠️ A strong earthquake near the sea is a warning to seek higher ground or evacuate inland to avoid tsunamis.
• 🌪️ Earthquakes and tsunamis are natural disasters that provide insights into Earth's structure and the importance of preparedness.

Q & A

What do earthquakes help scientists study?

Earthquakes help scientists study what is inside the Earth by generating seismic waves that provide information about the Earth's interior.

How do seismic waves form?

Seismic waves form when a fault suddenly moves, releasing stored energy from the focus in all directions.

What is the difference between body waves and surface waves?

Body waves move through the Earth's interior, while surface waves travel along the Earth's surface and are responsible for most of the damage caused by earthquakes.

What are the two types of body waves?

The two types of body waves are primary waves (P waves) and secondary waves (S waves or shear waves).

How fast do P waves travel and what do they indicate about the Earth's interior?

P waves travel at 1.6 to 8 kilometers per second and can pass through solids, liquids, or gases, indicating the nature and composition of the Earth's interior.

What is unique about S waves and their movement?

S waves can only pass through solids, moving slower than P waves, and they cause the first rolling motion during earthquakes.

What are the two types of surface waves and how do they move?

The two types of surface waves are Love waves (L waves or Q waves) and Rayleigh waves (R waves). Love waves move the ground horizontally, while Rayleigh waves move the ground elliptically, up and down and side to side.

Why are surface waves more destructive than body waves?

Surface waves are more destructive because they move slower and cause more intense shaking near the Earth's surface.

How do seismic waves help determine the Earth's layered structure?

Seismic waves speed up or slow down as they travel through different depths, reflecting and refracting at certain depths, which indicates that the Earth is layered.

What is a tsunami and how is it related to earthquakes?

A tsunami is a powerful wave caused by an underwater fault movement that affects the water above it. It is related to earthquakes as both are caused by the sudden movement of faults.

What should one do if they feel a strong earthquake near the sea?

If one feels a strong earthquake near the sea, they should treat it as a warning signal and run to the highest place they can find or evacuate further inland.