Chapter 1
Earth Science
Course: Elementary Education Multiple Subjects 7001
Subject: Elementary Education Science Subtest 7005
Chapter: Earth Science
The Earth system is composed of several interdependent components that interact dynamically to shape the planet. These include the geosphere (solid Earth), hydrosphere (all water), and atmosphere (the blanket of gases surrounding Earth). These systems operate both independently and collaboratively to sustain life and drive natural processes such as weather, climate, tectonic activity, and erosion.
1. Structure and properties of the solid Earth (Geosphere)
The geosphere refers to the solid portion of Earth, including rocks, minerals, soil, and the interior layers. The structure of the Earth is differentiated into several layers based on composition and physical properties.
- Crust The outermost solid layer of Earth. It is divided into continental crust, which is thicker and composed mostly of granite, and oceanic crust, which is thinner and composed mainly of basalt. The crust ranges from approximately 5 kilometers thick beneath oceans to about 70 kilometers thick beneath mountains.
- Mantle Located beneath the crust, the mantle extends to a depth of about 2,900 kilometers. It is composed primarily of silicate minerals rich in magnesium and iron. The upper part of the mantle, combined with the crust, forms the lithosphere. Below the lithosphere lies the asthenosphere, a ductile region that allows for the movement of tectonic plates.
- Core The core is divided into two parts: the outer core and the inner core. The outer core is liquid and composed mostly of iron and nickel. Its movement generates Earth’s magnetic field. The inner core is solid, also composed primarily of iron and nickel, and remains solid due to intense pressure despite its high temperature.
- Lithosphere and tectonic plates The lithosphere is broken into several tectonic plates that float on the asthenosphere. The movement of these plates causes geologic activity such as earthquakes, volcanic eruptions, and mountain formation. Plate boundaries can be divergent (plates move apart), convergent (plates move toward each other), or transform (plates slide past one another). For example, the Himalayas were formed by the convergence of the Indian and Eurasian plates.
- Rock cycle Rocks are constantly being formed, broken down, and reformed through the rock cycle. The three main types of rocks are igneous (formed from cooled magma or lava), sedimentary (formed from compacted sediments), and metamorphic (formed by heat and pressure acting on existing rock). Real-life applications include the use of granite for countertops (igneous), limestone in cement (sedimentary), and marble in sculpture (metamorphic).