Earth Science Mr. G. Yannakoulias

Present Day Planet Earth Earth as it appears from space at the present time It did not always look this way The age of Earth is about 4.5 billion years

The Birth of Planet Earth About 4.5 b.y.a. Our region of solar system was made of gas and dust debris from a star that existed in this region of the solar system but exploded in what is called a nova

Debris From Exploded Star Coalesced Over Time to form a “Planetesimal” Gravity caused the rock debris to coalesce and form larger bodies of rock called “planetesimals” Eventually this led to the formation of early planet Earth

Earth about 4.0 b.y.a. This process continued for about a billion years The Earth at this time resembled a hot ball of fiery lava

Cooling of Earth’s Surface Eventually Earth cooled enough to form a crust on its exterior surface

Formation of Earth’s Oceans Oceans were formed from Earth’s bombardment by comets that contain water hitting its surface This happened over many millions of years

Volcanism and Formation of Earth’s Oceans Volcanic activity on early planet Earth was frequent This resulted in the formation of water vapor which also helped to form oceans

Earth at about 2.5 billion years ago The Earth at this point was completely covered in water with very little if any land protruding

Formation of Land Masses Volcanic activity continued helping to form continents and islands that exist today The continents at that time did not look anything like they do today though

Earth’s Changing Surface Earths surface features are not static They are constantly changing even today The change is so slow however that we think that it is and has always been the same but this is a fallacy— fixism is the idea that the Earth has always looked the way it does today

Earth’s Changing Surface Over Time

How Do The Continents Move Around? If you can see the surface of the Earth you would notice that it is made up of a series of plates—sections of crust that are separate from each other These plates are where you find crustal sections of continents as well as crustal sections of ocean They move and slide past each other from pulling and pushing by forces below the Earth’s surface resulting in movement of continents or “Continental Drift”

Earth’s surface is made of plates

Alfred Wegener (1880-1930) Noticed that the edges of continents fit together like pieces of jigsaw puzzle He thought that continents were together in the past His researched proved this to be the case This was known as the Continental Drift Theory

Pangea Wegener formed a map of the early Earth which fitted all of the continents together This supercontinent is called Pangea

Wegener’s Hypothesis Met With Skepticism by Scientific Community Wegener’s hypothesis was initially rejected by the scientific community in spite of evidence He could not explain how continents could move which did not help him Furthermore, scientists could not imagine what forces were needed to allow continents to move Decades later it was revised and accepted after the discoveries of the ocean floor Wegener’s hypothesis was the beginning of the development of the theory of Plate Tectonics

Plate Tectonic Forces and Plate Movement Thick molten magma rises and falls due to convection Since it is thick (i.e. viscous) it pulls the plates on the Earth’s crust with it It even tears the crust in places as well

Your Task Read Pages 272-276 Make notes in your textbook on this material This will be your notes for this section of the course Hint: Use the same headings they use in your textbooks and just jot down the important information in the different sections