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A Changing Planet

        The Earth is always changing. Powerful forces shape our air,water and land, and will continue to transform our planet. 

        Plate tectonics, climate changes, and water circulation are the main processes that drive changes in Earth’s land, air, and oceans.           

        These changes can have both beneficial and harmful effects on Earth’s climate and biota. Earth's changes will also impact our future on Earth.

        Some of these changes are a natural part of the earth system, but the responsibility for other changes falls squarely on humanity’s shoulders.

Let´s explore three main forces that bring about Earth's changes.

SEASONS

   
Today, when people speak of climate change, they focus on changes in climate that result from human activity. But when scientists  became interested in climate they began to study the atmosphere.
        Natural climate variability results from fluctuations in the atmosphere. The driving force behind weather and climate is energy from the sun. Climate fluctuations can vary in length from hundreds of millions of years to one year, in addition to seasonal changes.
        Seasons are divisions of the year, defined by the position of the Earth in its orbit around the Sun. The seasons occur because of the tilt in the Earth´s axis with respect to tht plane of earth´s orbit.
        Except for solar radiation, the most important climate forcing agents arise from the greenhouse effect on outgoing infrared radiation.   



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Geography Seasons

WATER CYCLE - RUNNING WATER

        The hydrologic or water cycle involves the continuous circulation of water in the Earth-Atmosphere system.                                At its core, the hydrologic cycle is water, as a liquid or solid, changing into water vapor (a gas) and back into a liquid or solid. This change of state of water occurs in the atmosphere and between the earth's surface and atmosphere (from the ground to the atmosphere and back again).

        The vast bulk of the water in the water cycle is found in the oceans. The oceans hold 96.5% of the earth's water and due to their size it may take thousands of years for a water molecule to move from the ocean to the atmosphere. The water cycle hasbeen running on the Earth for billions of years, keeping the overall balance of water on Earth fairly constant.


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Where does water go when it rains?

INTERACTIVE FLASH PRESENTATIONS

 


Thirstin's   Water Cycle


PLATE TECTONICS - FORCES SHAPING EARTH

        The theory of plate tectonics states that Earth’s lithosphere consists of plates that ride on hotter, more mobile material. In Geology, a plate is a large rigid slab of solid rock. The word tectonics is derived from a Greek word meaning “to build” and refers to the deformation of Earth’s crust and the structural features that result.            Earth has seven large plates and a dozen or so smaller plates. Tectonic plates can move into, away from, or past one another. Therefore plate margins are some of the most geologically active parts of Earth’s surface.

         The forces that drive the movement of the plates are not precisely known, but they likely relate to convective movement within Earth’s mantle. Plates move from one to 13 centimeters per year. The movement of plates correlates directly with the prevalence of geologic hazards, so it is generally riskier to live near plate boundaries than on stable areas of the continents.



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FROM:


How the Earth was formed - The Power of the Planet

Earth Science:The World Below

Physical Geography - Forces that Shape Our Earth



CHECKING YOUR PROGRESS

 






 


 Vocabulary Games - Features of the Earth



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