ENRU

    Arrows to move, Enter to open

    Chalk

    A rock made of plankton that stores water like a sponge.

    Chalk in the atlas

    1. Atlas regionJerez-Xérès-Sherry
    2. Atlas regionChampagne

    Atlas regions where this rock appears in the text or the soil profile.

    Pick a place and the globe turns to it. You can also drag the globe.

    What it is

    Chalk is a kind of limestone made entirely of marine plankton, the tiny plates of coccolithophores.1

    chalk
    gravel
    clay

    Schematic: how fast water drains through the rock. A qualitative comparison based on the sources on this page.

    Water in reserve

    The chalk of Champagne is highly porous: a cubic metre holds 300 to 400 litres of water. It draws that water up by capillary action and keeps the vine supplied even in dry summers.2

    Geologist Alex Maltman notes that geology's main direct role is drainage combined with water storage, and that gravel, granite and chalk can all provide it.3

    Regions

    Sources

    1. Rock set general cards (education resource). The Geological Society of London. level 4 · checked 2026-10-13
    2. Champagne and its soil. Comité Champagne. level 4 · checked 2026-10-13
    3. On rocky ground: The science of soil and wine taste (Prof. Alex Maltman). Decanter, 2018. level 4 · checked 2026-10-13