Joints are fractures in rocks along which no differential displacement has occurred.  This distinguishes them from faults, along which displacement has taken place.
<p>Some joint surfaces have feathery-like features called plumose markings.  They consist of an axis and small-scale, radiating-outward ridges.  The divergent-direction axis points toward the direction of fracture propagation.
</p><p>Host rock: Columbus Limestone, Middle Devonian
</p>
Locality: trailside, Level 3 of Seneca Caverns, just south of Flat Rock Quarry &amp; south-southwest of the town of Bellevue, northern Ohio, USA
James St. John
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