Comets are celestial objects consisting of a nucleus made up of ice and dust, a head, and when near the sun, a tail of gas and dust streaming outwards. There are two types of comets, short-period and long-period comets. Short-period comets reside in an icy region called the Kuiper Belt and orbit the sun in less than 200 years. On the other hand, long-period comets are found from 5 thousand to 100 thousand astronomical units from the sun and they have very long, unpredictable orbits. The coma of a comet is formed when nears the sun and an atmosphere develops around the comet. The coma could be many, many kilometers in diameter. Comets are not able to support life themselves, but they have brought the building blocks of our life through impacts with Earth. One example of a comet is Comet Halley, which makes a complete orbit around the Sun in 76 Earth years, which means it is a short-period comet.
Ch.3 Lesson 2
Topography is the shape of the land. The topography of an area includes the area’s elevation, relief, and landforms. Elevation is the height above sea level at a point on Earth’s surface. The elevation of Florida is sea level. The relief of a land is the difference in elevation between the highest and lowest parts of an area. Mountains are an example of high relief. Lastly, landforms are features of topography formed by the processes that shape Earth’s surface. An example is a hill, or a valley. The major types of landforms are plains, mountains, and plateaus. Plains are landforms made up of nearly flat or gently rolling land. They have low elevation and low relief. Mountains are landforms that are made of rock and are shaped by erosion, deposition, and weathering. They have high elevation and high relief. Plateaus are landforms that are shaped by weathering and have flat surfaces. They have high elevation but low relief. The last topic of this lesson is landform regions, which are areas of land made up of one type of topography. An example of a landform region is the Rocky Mountains, which are made up of mountain ranges.
Ch.7 Lesson 2
A system is a group of parts that work together to