Memory Mixtures and Soil MemoryVersión en línea Match the vocabulary word to the definition. por Michael Porter A mixture of water, air, tiny pieces of rock, and humus weathering The upper layer of soil in which plants have most of their roots clay Particles of rock that are smaller than sand but larger than clay silt The largest particles of rock that make up soil the remains of decayed plants or animals in the soil The breaking down of rocks on Earth’s surface into smaller pieces mixture The smallest particles of rock that make up soil decay humus To be slowly broken down by the natural processes that destroy a plant or body a combination of two or more different substances that keep their identities topsoil soil physical property A characteristic of matter that you can observe or measure directly sand