What does cataclastic mean?
Cataclastic is an adjective used almost exclusively in geology to describe rock that has been physically broken down — crushed, fractured, and granulated — by intense mechanical forces, most often along fault zones where large blocks of the Earth's crust grind past one another. A cataclastic rock retains its original minerals but their grains are shattered and reassembled into a fragmented, sometimes powdery texture; cataclastic breccias, made of angular broken fragments, are a classic example. The term contrasts with textures produced by chemical alteration or by heat-driven recrystallization, and it signals brittle rather than ductile deformation. Though it sounds dramatic, echoing words like 'cataclysm', it is a precise scientific descriptor rather than a figure of speech. For students of earth science, it is essential vocabulary for interpreting the history of deformation recorded in deformed rocks.
adjective(Of rock) having a texture or structure produced by the mechanical crushing, fracturing, and granulation of mineral grains, typically during intense deformation along faults.
- (Geology) Describing rock that has been deformed by fracturing, crushing, and granulation of its constituent grains, as in fault zones.
- More broadly, describing structures or processes involving mechanical fragmentation of rock rather than chemical change.
"The fault zone was filled with a dark cataclastic breccia ground from the surrounding granite."
"Under the microscope, the quartz grains showed a distinctly cataclastic fabric, evidence of the immense pressures along the ancient thrust fault."
"Mylonites are distinguished from cataclastic rocks by the ductile, rather than brittle, nature of their deformation."
The same ancient Greek root that gives us 'cataclysm' — 'a washing away' — also powers 'cataclastic', the word geologists use for rocks that have been literally crushed to bits by moving faults.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cataclastic
Cataclastic derives ultimately from the Greek verb 'klan' (or 'klaein'), meaning 'to break', combined with the prefix 'kata-' ('down'). It entered scientific English in the nineteenth century alongside the related noun 'cataclasis', as geologists formalized terms for rocks deformed by crushing. The same breaking root underlies 'clastic' (applied to fragmental sedimentary rocks), 'iconoclast' ('image-breaker'), and 'cataclysm' (via a related sense of overwhelming destruction).
Related word forms
How cataclastic is actually used
Strictly a technical term used in structural geology and petrology; it rarely appears outside scientific writing. It carries no figurative or informal use, despite its resemblance to everyday words like 'cataclysmic'.
Easily confused with cataclastic
'Cataclysmic' describes a disastrous, violent upheaval in general usage, while 'cataclastic' is a technical geology term describing rock textures formed by mechanical crushing.