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

[Music] hi there in our previous video we've talked about faults and earthquakes if you haven't watched it yet you can pause this video and watch that one first to better understand our lesson today did you know earthquakes help scientists with their studies earthquakes help them figure out what is inside the earth as you've learned from our previous lessons when a fault suddenly moves an earthquake is generated the shaking starts from the focus and spreads out you can get an idea of how this happens by dipping your finger on stagnant water see the ripples that move out in circles the vibrations are something like that the vibrations are more properly called seismic waves as the rocks slip and slide the stored energy is released from the focus in all directions these seismic waves are detected measured and recorded by an instrument called the seismograph the data are recorded on a strip of paper called the seismogram there are two types of seismographs horizontal a scene on the left and vertical as seen on the right we will be discussing how seismographs work in another video for now we will be focusing on seismic waves and how it provides information about the earth's interior alright so there are two main types of seismic waves the body waves and the surface waves body waves are further classified as either primary waves also called p waves and secondary waves also called s waves or shear waves on the other hand surface waves are further classified as love waves also called l waves or q waves and rayleigh waves also call this r waves let's talk about body waves first body waves move through the earth's interior they can provide scientists with information regarding the nature and composition of it they also enable seismologists to locate the focus or the epicenter p waves are the fastest moving waves traveling at 1.6 to 8 kilometers per second they are the first to arrive in seismograph readings they can simply pass through any material solids liquids or gases they can move even through earth's inner and outer cores they move tiny rock particles back and forth as they travel through rocks in a compressive manner p waves are longitudinal waves these waves arrived at the surface like a sudden quick thud they are also called compressional waves and are actually sound waves on the other hand s waves can pass only through solids and move slower than p waves shearing is not transmitted in liquids or gases they don't pass through earth's outer core they are transverse waves and as they move they displace rock particles outward pushing them perpendicular or 90 degrees to the path of their motion the first period of rolling during earthquakes is always associated with s waves they do not move straight through the earth much of the destruction near the focus of an earthquake is the result of the stronger shaking caused by s waves now let's move on to surface waves surface waves arrive only after body waves they are entirely responsible for most of an earthquake's damage and carnage they move elliptically in a vertical plane or sideways in a horizontal plane they travel slower than body waves the most intense shaking comes near the end of an earthquake love waves also known as l waves or q waves are the fastest surface waves they move the ground from side to side producing horizontal motion typical velocities range between two to six kilometers per second rayleigh waves or r waves roll elliptically along the ground they move the ground up and down and side to side in the same direction of its propagation most of the shaking felt from an earthquake is due to this wave it is the slowest of surface waves its speed ranges from one to two kilometers per second now how do seismic waves give us information about the earth's interior as body waves travel deeper into the crust they speed up this means that at a certain depth the rocks are denser in the upper part of the mantle the waves slow down this means the rocks there are partially molten as the waves reach the core the s waves disappear this means that the outer core is liquid at certain depths the waves are reflected and refracted this makes us conclude that the earth must be layered thus earthquake waves give us a picture of the earth's interior in the same way an ultrasound provides an image of a baby inside the womb alright so that's all we need to know about seismic waves and earth's interior for now [Music] but since we are in a topic of earthquakes let's discuss a bit on how earthquakes lead to tsunamis faults are found not only on land but also under the sea when a fault at the bottom of the sea suddenly moves the water above it can be affected a sudden push from an underwater fault can produce a wave called a tsunami unlike a wave that is formed by the wind a toonami is so much more powerful wind waves are just sea surface waves in comparison a tsunami involves the whole death of the sea from the sea floor to the surface far from the shore a toonami is low maybe just a meter high but it travels at the speed of a jet plane when the tsunami reaches the shore it slows down but it grows in height [Music] take note that not every fault movement beneath the sea will produce a toonami faults that move in a horizontal direction or sideways will not result in a toonami default has to move vertically for a toonami to happen a tsunami is very destructive because the force of the whole ocean is behind it this is the reason why whole towns and cities are totally devastated after a tsunami attack thus when you are near the sea and you feel a strong earthquake treat that as a warning signal run to the highest place you can find or if you have a vehicle evacuate further inland so let's wrap things up when a fault suddenly moves on land you get an earthquake but if a fault suddenly moves in or near a body of water you may get a tsunami in addition to the earthquake earthquake waves provide information about the interior of the earth through seismic waves seismic waves travel through the body of the earth at certain deaths the waves are reflected and refracted this means that the earth must be layered that's all for now we will be discussing about typhoons in our next lesson see you on our next video and don't forget to keep your minds busy if you like this video please subscribe to our channel and hit the notification icon for more videos like this

Channel: The Learning Bees

Views: 86,170

Keywords: The Learning Bees, Department of Education, DepEd, MELC-Based, Most Essential Learning Competencies, Science, Grade 8, MELC, Earthquakes, Faults, Tsunami, Seismic Waves, Interior of the Earth, Seismograph, Seismogram, How Earthquakes provide information about the Earth's Interior, P-Waves, S-Waves, L-Waves, R-Waves, Rayleigh waves, Love Waves, Primary Waves, Secondary or shear waves, Body waves, Surface Waves, How an earthquake leads to tsunami, Types of seismic waves, Earthquake waves

Id: WUv5bLI2W0Y

Length: 9min 26sec (566 seconds)

Published: Fri Nov 27 2020