What is the Lithosphere?
What we’ll explore in this module
In this module, we’ll review the basics of Earth’s geosphere, or all of Earth’s solid materials. We’ll discuss Earth’s inner structure and the geologic cycle, meaning the many interactions (internal and external) that shape earth’s crust. Then, we will discuss Earth’s rock cycle, which is a major part of the geologic cycle showing the continuous alteration of Earth materials into different types of rock.
What is the Lithosphere?
The Earth-Atmosphere interface is the meeting place of the internal and external processes that both build up and wear away landscapes. These landscapes largely are considered part of Earth’s geosphere –the solid, inorganic part of Earth, essentially comprising all solid Earth materials (rocks, minerals, soils, landforms, magma, fossils, and so on). Within the geosphere is the lithosphere, which is Earth’s rigid, outer shell.
Broadly speaking, geology is the study of the geosphere. Geology studies all aspects of Earth including its history, composition and internal structure, surface features, and the processes acting on them. Geomorphology is a subfield of both physical geography and geology studying the origin, evolution, form, and distribution of Earth’s landforms.
Earth’s geosphere overlaps and interacts with all of Earth’s other systems – the biosphere, atmosphere, and hydrosphere.
Geologic Cycle
The geologic cycle is made up of the internal and external interactions that shape Earth’s crust. Earth’s geologic cycle interacts with numerous other cycles and systems, such as the tectonic and rock cycles (which we will get to soon).
The geologic cycle also interacts with the hydrologic cycle – consider subsurface mechanisms like groundwater flow and aquifer recharge, as well as fluvial geomorphology and interactions between surface streamflows, rocks, and sediments!
Endogenic and Exogenic Systems
Earth’s geologic system can be divided into two processes: Exogenic and Endogenic.
The exogenic system involves all processes operating at Earth’s surface. These are largely driven by solar energy and the movement of air, water, and ice. In other words, this is where much (though not all) of the geologic system’s interactions with the Biosphere, Atmosphere, and Hydrosphere occur.
The endogenic system involves all processes operating in Earth’s interior. These processes are driven by heat and radioactive decay, which keep the lower mantle soft and flowing. The lower mantle is unevenly heated by the decay of unstable radioactive elements, contributing to the uneven molten patterns which drive convection currents.