1. UNIT 1. THE EARTH’S STRUCTURE AND DYNAMICS

2. THE EARTH’S STRUCTURE

3. The Earth was formed 4,570 million years ago. Initially, our planet was extremely hot and it was molten. This is the reason why the heavy elements sank, and the light elements emerged, what gave the Earth a heterogeneous structure divided into different layers.

6. The core is made up of iron and nickel. The outer core is liquid and the inner one is solid. This difference of viscosity can be the reason of the Earth´s magnetic field. The mantle is around the core and it is the wider layer, which is made up of silicates. And the last layer is the crust, which is floating over the mantle due to its low density. On this layer we can find oceans and continents. The first oceans were formed 3,850 million years ago.

7. How do we know about the earth’s structure?  Earth’s density compared to granite  Study of seismic waves

8. D= Mass / Volume Earth radius= 6370 Km Earth mass= 5,97 x 10 24 kg Granite density= 2,7 g/cm 3 Calculating Earth density

9. Seismic waves are waves of energy that travel through the Earth's layers as a result of an earthquake earthquake

10. Primary waves (P-waves) are compressional waves that are longitudinal in nature. P waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first, hence the name "Primary". These waves can travel through any type of material, including fluids, and can travel at nearly twice the speed of S waves.longitudinal

11. Secondary waves (S- waves) are transverse in nature. Following an earthquake event, S-waves arrive at seismograph stations after the faster- moving P-waves and displace the ground perpendicular to the direction of propagation. S- waves can travel only through solids.transverse

12. THE EARTH’S DYNAMICS

13. Continental Drift theory Alfred Wegener developed the Continental Drift theory.

14. Continental Drift theory Wegener thought all the continents were once joined together in one supercontinent (Pangaea) before breaking up and drifting to their current positions. Wegener thought all the continents were once joined together in one supercontinent (Pangaea) before breaking up and drifting to their current positions.

15. Continental Drift Theory

16. Continental Drift theory Wegener tried to support his theory with evidence. Four pieces of evidence: Geographic Geologic Paleoclimatic Biological

17. Continental drift theory Geographic evidence: the shape of some continents matches.

18. Continental drift theory Geologic evidence: similar rock formations are found on different continents. Geologic evidence: similar rock formations are found on different continents.

19. Continental drift theory Paleoclimatic evidence: in the past the climate of some continents was different, as if they had been in a different position.

20. Continental drift theory Biological evidence: look-alike animals and plant fossils are found on different continents. Biological evidence: look-alike animals and plant fossils are found on different continents.

21. Continental drift theory Wegener wasn´t able to explain why the continents moved throughout time. Therefore, scientists of his time didn´t accept his theory.

22. Continental drift theory https://www.youtube.com/watch?v =_5q8hzF9VVE https://www.youtube.com/watch?v =_5q8hzF9VVE

23. The plate tectonics theory In 1950 the plate tectonics theory was developed. This theory could explain the movement of continents so Wegener´s ideas were rediscovered.

24. The plate tectonics theory The Earth is a dynamic planet. Even if the mantle is solid, the high temperatures make it plastic and make possible some kind of flow of heat inside it. This is what we call convection currents and they are related to the continental drift. The lithosphere is made up of the crust and the outer part of the mantle. This layer is broken up into fragments called plates. These plates interact and are responsible for the internal geologic processes.

25. Tectonic plates https://www.learner.org/interactives/dynamicearth/plate.html

26. Plates and boundaries A convergent boundary occurs where two plates are pushing toward each other. Crust is destroyed.

27. Plates and boundaries A divergent boundary marks two plates that are moving apart from each other. New crust is formed.

28. Plates and boundaries A transform boundary occurs where two plates slide past each other.

29. The Seafloor Spreading The Seafloor Spreading (in divergent boundaries), together with the Continental Drift theory, were the base for the Plate Tectonics theory.

30. Plate tectonics theory https://www.youtube.com/watch?v=ZTRu6 20bIsE https://www.youtube.com/watch?v=ZTRu6 20bIsE