The Four Houses (and Elements) of Hogwarts - Hufflepuff (Earth)
Earth is not just the name of an element, but also of our planet – even though 70% of its surface is covered in water. But humans are land animals, and earth is, literally, home. Another word for the element earth is soil – the different layers of minerals mixed with organic matter that cover the planet's crust. Soil consists of the layers surface horizon, subsoil, substratum, and beneath that, hard bedrock. Many people think of humus (Latin for earth, ground) when speaking of earth – the typically black, organic horizon on the top surface, produced by compost. Yet this layer only makes up five percent (or less) of the soil. The different types of soil are defined by various factors, such as texture, structure, density, porosity, and colour. According to these properties they are categorized as clay, loam, sand, silt, or any combination thereof. All these soil types are built by the so called parent materials – minerals such as quartz, calcite, or feldspar. These minerals on the other hand derive from rocks, either of igneous (cooled lava or magma (Latin ignis = fire), sedimentary (formed by the deposition of minerals and organic matter on the surface of the earth or in bodies of water), or metamorphic (minerals changed physically and/or chemically through heat and pressure) origin. Metals are sometimes counted as being a form of element earth, sometimes seen as a separate element (as in the Chinese five element philosophy).
Since earth is our home and we walk/sit/lie on it all of the time, it makes sense that earth stands for stability, safety, and steadiness. Of course this is an illusion, as earthquakes teach us, but it seems to be a necessary one for humans. In many mythologies humans themselves are said to be made of earth – in Christian mythology, the first human Adam (Hebrew adamah = earth, ground) is formed from clay. In Greek mythology, Deukalion, the son of Prometheus, and his wife Pyrrha, the daughter of Pandora, were the only survivors of a deluge sent by Zeus. When asking the oracle of Delphi how to repopulate the earth, they were told to throw the bones of their mother over their shoulders – leading them to cast stones (the bones of earth) over their shoulders, which then turned into men and women, respectively. Latin homo – human, is derived from humus – earth. The same word root can be found in Old English guma, Old High German gomo, Old Norse gumi, Gothic guma, and Old Lithuanian žmuō, meaning man, human (all from Indo-European *dheĝhom – earth, also leading to Old Greek χθών/khthon, and Sanskrit kṡam, both meaning earth).
Even with earthquakes and mudslides, earth is the most static element. In contrast, all other elements are in constant movement. Similarly, earth is the heaviest element and the only element of a constant solid aggregate state (water can temporarily be solid in the form of ice). Because of this, and the fact that all commodities are found in and on the earth (except water), earth is connected to richness, wealth, and materialism (the natural opposite to air as the element of immaterial richness in the form of thought and ideas). Old Greek πλούτος/ plútos - wealth is cognate to Latin Pluto, the god of the underworld. His wife, Proserpina (Old Greek Persephone), and her mother Ceres (Old Greek Demeter) symbolises another aspect of earth – fertility. The importance of this increased with the rise of sedentariness during the neolithic in almost the whole world. Staying in one place meant that people's life depended on the fertility of the soil. So naturally earth deities can be found in all mythologies of the first farmers.
While air and fire are connected with the human spirit, and water literally is the blood in our veins, earth's anatomical parallel are flesh and bones – in other words, the most substantial matter of the human body. The younger Edda describes how the blood of the first being, the giant Ymir, became the ocean, while his flesh became earth and his bones became rocks. Snorri Sturluson also writes in the prologue of the younger Edda: “It is the third property of the earth, that when it is opened and dug, then vegetation grows on the soil which is uppermost on the earth. Rocks and stones they (mankind) thought of as equivalent to teeth and bones of living creatures.”
Hufflepuffs are loyal, hard working, honest/true, fair-minded, and patient. Their work ethic fits perfectly with the connection between earth and toil – a quote from the Bible illustrates this nicely: “By the sweat of your brow you will eat your food until you return to the ground, since from it you were taken; for dust you are and to dust you will return." (Genesis 3:19). Likewise, to be down-to-earth means to see things practical and not to shy from problem solving. Loyalty, justice, and honesty (the first sorting hat's song says “Those patient Hufflepuff are true...”, which can be either interpreted as being honest, having integrity, or both.) go well with the inflexible and solid aspect of earth (to be as solid as a rock, to be set in stone). Related to this is conservation, which explains the valuing of the past and traditions, mentioned to be a Hufflepuff (and Slytherin) trait on Pottermore. Patience goes with the slow-to-move trait of earth (contrasting with the fiery temper associated with Gryffindor).
Huffelpuff's mascot, the badger, builds large tunnels (called a sett) beneath the earth and is a cautious, quiet animal, unless attacked. As was stated recently on Pottermore, Hufflepuff's colours black and yellow symbolise soil and wheat (prior to this information my guess would have been soil and sand). Unsurprisingly the common room is located underground, with round doors and windows, being reminiscent of a hobbit hole. It is also near the kitchens and is decorated with lots of plants, representing the nurturing/fertile aspect of earth.