Planet Earth

How old is the Earth? :10 0 of million years million years 3.1 billion years billion years 5.13 billion years

The Early History of the Earth Earth formed 4.6 billion years ago from the inner solar nebula. Four main stages of evolution:

What is “differentiation”? :10 0 of The mixing of substances. 2.Lighter substances sinking to the bottom, while heavier substances rise to the top. 3.Heavier substances sinking to the bottom, while lighter substances rise to the top. 4.The chemical change of substances near the surface of a planet due to chemical reactions with the atmosphere. 5.The chemical change of substances near the core of a planet induced by great heat

The Early History of the Earth Earth formed 4.6 billion years ago from the inner solar nebula. Four main stages of evolution: Two sources of heat in Earth’s interior: Potential energy of infalling material Decay of radioactive material Most traces of bombardment (impact craters) now destroyed by later geological activity

What killed the dinosaurs (according to the most widely accepted theory)? :10 0 of Global climate change caused by variations in the sun’s energy output. 2.Global climate change caused by a massive meteorite/comet impact. 3.A reptile dysfunction. 4.A nearby stellar explosion (supernova / gamma-ray burst). 5.Nothing. They still exist (see, e.g., Jurassic Park)!

Meteorite Impacts on Earth Over 150 impact craters found on Earth. Most famous example: Barringer Crater near Flagstaff, AZ:

Impact Craters on Earth Barringer Crater: ~ 1.2 km diameter; 200 m deep Formed ~ 50,000 years ago by a meteorite of ~ 80 – 100 m diameter

The Chicxulub Crater This impact may have caused major climate change, leading to the extinction of many species, including dinosaurs. extinction of many species, including dinosaurs Much larger impact features exist on Earth: Impact of a large body (comet nucleus?) formed a crater ~ 180 – 300 km in diameter in the Yucatán peninsula, ~ 65 million years ago:

Seismic waves are bent or bounce off transitions between different materials or different densities or temperatures. Earth’s Interior Direct exploration of Earth’s interior (e.g. drilling) is impossible. Earth’s interior can be explored through seismology: Earth quakes produce seismic waves.

If you are standing next to railroad tracks and you don’t see or hear a train, you can tell if there’s a train approaching by putting your ear on the tracks. This works because … :10 0 of your visual abilities improves when you block one of your ears. 2.sound waves travel more rapidly along the tracks than through the air. 3.Sound waves get less absorbed when traveling along the tracks than through the air. 4.All of the above and

Earth’s Interior (II) Earth’s interior gets hotter towards the center. Earth’s core is as hot as the sun’s surface; metals are liquid near the core. Basic structure: Solid crust (light [Si-based] materials) Solid mantle (light elements, iron-poor) Liquid core (iron-rich) Solid inner core (iron-rich)

Earth’s Magnetic Field Convective motions and rotation of the core generate a dipole magnetic field Earth’s core consists mostly of iron + nickel (materials that magnets are made out of)

The Role of Earth’s Magnetic Field Earth’s magnetic field protects Earth from high-energy particles coming from the sun (solar wind). Surface of first interaction of solar wind with Earth’s magnetic field = Bow shock Region where Earth’s magnetic field dominates = magnetosphere Some high-energy particles leak through the magnetic field and produce a belt of high-energy particles around Earth: The Van Allen belts

Which phenomenon is caused by the interaction of energetic particles from the sun with Earth’s magnetosphere? :10 0 of Northern lights (aurora borealis). 2.Sun spots. 3.Prominences. 4.Hurricanes. 5.Earthquakes

The Aurora (Polar Light) As high-energy particles leak into the lower magnetosphere, they excite molecules near the Earth’s magnetic poles, causing the Aurora

Tectonic Plates Earth’s crust is composed of several distinct tectonic plates, which are in constant motion with respect to each other → Plate tectonics

Tectonic Plates (II) Evidence for plate tectonics can be found on the ocean floor … and in geologically active regions all around the Pacific

Geological activity around the Pacific Volcanism: Mt. St. Helen Earthquakes: Kobe (Japan) Volcanism: Pinatubo (Philippines) Earthquakes: San Francisco

The major Tsunami of 2004 in the Indian Ocean was caused by tectonic activity at the boundary between … :10 0 of 116 1)the African and the Indian- Australian Plates. 2)the Indian-Australian and Eurasian Plates. 3)the African and the Arabian Plates. 4)the Arabian and the Indian- Australian Plates. 5)the African and Antarctic Plates

Plate Tectonics Tectonic plates move with respect to each other. Where plates move toward each other, plates can be pushed upward and downward → formation of mountain ranges, some with volcanic activity, earthquakes Where plates move away from each other, molten lava can rise up from below → volcanic activity

Active Zones Resulting from Plate Tectonics

The interaction between the Pacific and the North American Plates is responsible for the formation of :10 0 of 116 1)the Hawaiian Islands. 2)the Alps. 3)the Rocky Mountains. 4)the Andes. 5)the Appalachian Mountains

Volcanism on Earth (I) Volcanism on Earth is commonly found along subduction zones (e.g., Rocky Mountains). This type of volcanism is not found on Venus or Mars. not found on Venus or Mars. Subduction Zones Example: Stromboli (Sicily, Italy, 1998)

Hawaii is also very volcanically active. Is this also because Hawaii is located at a plate boundary? :10 0 of 116 1)Yes, it is located at the boundary of the Pacific plate. 2)Yes, it is located at the boundary of the North American plate. 3)Yes, it is located at the boundary of the Eurasian plate. 4)No. This must be a different kind of volcanic activity. 5)No. Hawaii is not volcanically active

Shield Volcanoes Found above hot spots: Fluid magma chamber, from which lava erupts repeatedly through surface layers above. All volcanoes on Venus and Mars are shield volcanoes Volcanism on Earth (II)

Shield Volcanoes (II) Tectonic plates moving over hot spots producing shield volcanoes → Chains of volcanoes Example: The Hawaiian Islands

Earth’s Tectonic History

Earth’s Tectonic History (II)

History of Geological Activity Surface formations visible today have emerged only very recently compared to the age of Earth.

Guess: How thick is the Earth’s breathable atmosphere (beyond which you would need oxygen masks to breathe), compared to the Earth’s radius? :10 0 of 116 1)1/24,000 Earth radius. 2)1/800 Earth radius. 3)1/15 Earth radius. 4)1 Earth radius. 5)10 Earth radii

Earth’s Atmosphere Only about 1/800 of the Earth’s radius!

Which is the most common gas in Earth’s atmosphere? :10 0 of 116 1)Oxygen 2)Nitrogen 3)Carbon dioxide 4)Methane 5)Water vapor

The Atmosphere Earth had a primeval atmosphere from remaining gasses captured during formation of Earth

Do you think that the Earth’s atmosphere is still very similar to what it was about 4 billion years ago? :10 0 of 116 1)Yes 2)No

The Atmosphere Atmospheric composition severely altered (→ secondary atmosphere) through a combination of several processes: Earth had a primeval atmosphere from remaining gasses captured during formation of Earth

Sources of Atmospheric Gas Outgassing: Release of gasses bound in compounds in the Earth’s interior through volcanic activity Later bombardment with icy meteoroids and comets

Loss of Atmospheric Gas Chemical reactions in the oceans Energetic radiation from space (in particular, UV)

Which of these processes might be the main reason that Mercury has almost no atmosphere? :10 0 of Thermal Escape 2.Stripping by energetic radiation from space 3.Condensation 4.Chemical reactions 5.Ejection by impacts

Which of these forms of radiation from space can reach the Earth unabsorbed? :10 0 of 116 1)Radio waves. 2)Infrared light. 3)Ultraviolet light. 4)X-rays. 5)Gamma-rays

The Electromagnetic Spectrum Need satellites to observe Wavelength Frequency High flying air planes or satellites

The Interactions between Light and Molecules X-rays 1) Splitting up molecules into atoms: Nitrogen (N 2 ) / Oxygen (O 2 ) 2) Ionizing (kicking electrons out of) atoms or molecules

The Interactions between Light and Molecules Ultraviolet Splitting up molecules, in particular, Ozone: Ozone (O 3 ) Oxygen (O 2 )

Why is the totally eclipsed moon visible at all (in a faint red glow)? :10 0 of 116 1)Because it is still glowing from the intense light it received during full moon before the eclipse. 2)Because it is illuminated by sunlight reflected off other terrestrial planets. 3)Because it is illuminated by sunlight scattered within the Earth’s atmosphere. 4)Because it is very shy during the eclipse and turns red when you are looking at it. 5)None of the above: The totally eclipsed moon is completely black

The Interactions between Light and Molecules Penetrates through the atmosphere mostly unabsorbed, but can get scattered: Visible Light This is why the sun appears red at sunrise and sunset; and why the sky is blue (if it’s not cloudy)

The Interactions between Light and Molecules Carbon dioxide (CO 2 ) / Water vapor (H 2 O) / any other asymmetric molecules (greenhouse gases) Infrared Causes asymmetric molecules to rotate This is the essential step of the Greenhouse Effect!

We know that UV and X-ray radiation from space is heating the atmosphere. Thus, do you expect that the atmosphere becomes hotter or colder with height, very high above the ground? 1)Hotter with increasing height. 2)No temperature change. 3)Colder with increasing height. :

The Temperature Structure of Earth’s Atmosphere Exosphere: Heated by UV and X-rays from space Thermosphere: Heated by X-rays from space Stratosphere: Heated by UV radiation from space Troposphere: Heated by greenhouse effect Ozone Layer Atmosphere gets colder at larger distance from heat sources. Top of Ozone Layer Temperature Altitude