The changing Earth Flashcards
What can we tell about the Earth from it’s rocks?
The Earth must be older than it’s oldest rocks which are about 4 thousand million years old, we can also tell that mountains are continuously forming as continents would be worn down to sea level
What is Wegener’s theory of continental drift?
He believes there was a single land mass that has since split into several continents which have drifted apart, it is supported by the way rocks fit together.
Why was his Wegener’s theory rejected at the time?
There were already other simpler theories, nobody could explain or measure the movements of the continents, he was not a trained geologist
How much does the sea floor spread each year?
The seafloor spreads a few centimetres a year
What occurs at the edges of tectonic plates?
Earthquakes, volcanoes and mountain building generally occurs at the edge of tectonic plates
What are P-waves?
P-waves are longitudinal waves which travel through solids and liquids
What are S-waves?
S-waves are transverse waves which travel through solids but not liquids
How can P and S waves be felt across the planet
P-waves can travel through the core and so can be detected all across the world, S-waves only go through the solid crust and parts of the mantle and so can only be felt in some parts of the world
What is the equation for distance of waves?
Distance (m) = wave speed (m/s) * time (s)
What is the frequency of waves?
The number of waves each second that are made by the source, hertz (Hz)
What is the amplitude of a wave?
The maximum displacement to the undisturbed position
How does amplitude and wavelength affect the how you hear a sound?
A sound is louder if it has a larger amplitude
A sound is higher pitched if it has a shorter wavelength
