Tutor profile: Abdelrahman Samir A.
Why is total mass of Earth is almost constant over time?
That's primarily due to a well know process called Plate Tectonics. Think of it as an onion layer theory of different densities. So the Earth is composed of different layers of different density, and the uppermost layer "Crust" is floating over the underlying viscous layer "Mantle" and that caused those plates in the crust level to compress together and destruct and melting to the lower mantle layer. Now on the other side of those colliding plates a separating space is produced causing the magma to rise up in between building new crust. And that's why the total mass is almost constant almost over the last 5 billion years.
How many vowels in the Arabic language?
Basically they are 3 vowels: A as in apple, O as in Omicron, E as in Elephant but those 3 vowels can be extended to be like Aa, Oo and Ee depending on the context. Vowels in Arabic can be used as well for stressing some kind of intonation, by adding them to different litters.
Subject: Earth Science
What is seismic waves?
Seismic waves is basically mechanical waves so it needs media to propagates within. So, for example; since air is the media of propagation of sound waves (another kind of mechanical waves), the underlying rocks is the media of propagation of sound waves. Seismic waves can occurs naturally in the case of earthquakes and we induce it to the subsurface it can help us understand the image of the subsurface and that's called exploration seismology.
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