| 1 | abrasion | wear caused by repeated rubbing or scraping | Hard |
| 2 | accretion | growth through gradual addition of material | Hard |
| 3 | aerosol | a gas containing suspended droplets or tiny solid particles | Hard |
| 4 | albedo | the fraction of light a surface reflects | Hard |
| 5 | aquifer | an underground layer that stores or carries water | Hard |
| 6 | arid | having very little moisture or rainfall | Hard |
| 7 | buoyancy | the upward force that supports an object in fluid | Hard |
| 8 | combustion | a burning reaction that releases heat | Hard |
| 9 | condensation | the change from gas to liquid | Hard |
| 10 | convection | transfer of heat through moving fluid | Hard |
| 11 | crust | the outer solid layer of a planet | Hard |
| 12 | crystalline | having atoms arranged in a regular pattern | Hard |
| 13 | delta | land built from sediment at a river mouth | Hard |
| 14 | discharge | the flow rate of water past a given point | Hard |
| 15 | drought | a long period with too little rainfall | Hard |
| 16 | geochemical | related to chemicals in Earth's materials | Hard |
| 17 | hydrology | the study of water and its movement | Hard |
| 18 | impermeable | not allowing liquid to pass through easily | Hard |
| 19 | isotope | a form of an element with a different neutron count | Hard |
| 20 | landform | a natural shape of the land surface | Hard |
| 21 | magma | molten rock beneath Earth's surface | Hard |
| 22 | mantle | the thick layer between a planet's crust and core | Hard |
| 23 | moraine | rock and soil left behind by a glacier | Hard |
| 24 | permeable | allowing liquid to pass through | Hard |
| 25 | precipitation | water falling from the atmosphere | Hard |
| 26 | reservoir | a place where water or another material is stored | Hard |
| 27 | salinity | the amount of dissolved salt in water | Hard |
| 28 | seismic | related to earthquakes or ground vibrations | Hard |
| 29 | stratum | one layer of rock or other material | Hard |
| 30 | subduction | movement of one crustal plate beneath another | Hard |
| 31 | turbulence | irregular, swirling movement of a fluid | Hard |
| 32 | watershed | land that drains into one river system | Hard |
| 33 | altitude | height above a reference level | Hard |
| 34 | capillary | a very thin tube through which liquid can move | Hard |
| 35 | coastal | located near the sea | Hard |
| 36 | insulate | to reduce the movement of heat or electricity | Hard |
| 37 | refraction | the bending of a wave as it enters a new medium | Hard |
| 38 | soluble | able to dissolve in a liquid | Hard |
| 39 | viscosity | a fluid's resistance to flowing | Hard |
| 40 | sublimation | a solid changing directly into gas | Hard |