The Vibrano Expanse is an unusual geological feature located in the lowlands of Ventral H4. The Expanse is best known for the eerie sensation it induces in sentient creatures - especially the very perceptive Rostran peoples - as well as the unusually regular pattern that its barren, light-colored hills form across the landscape.
The Vibrano Expanse consists of a series of hill ranges that span nearly 20 miles in both directions. These hills are regularly spaced resembling ripples in the surface of water when viewed from above, despite eons of erosion due to circumvection, the passage of rivers between them, and the geological activity inherent to the Ventral Tesseract. The soil of the Vibrano expanse is bright and shimmers in the daylight because of its high quartz content, a factor which may also contribute to the unusual sonic quality that the region is said to possess (see Localized Phenomena).
Despite the presence of rivers, billabongs, and seasonal pools among the hills, the Vibrano Expanse is somewhat barren. Some plant life does eke out an existence in the low spots between hills, providing habitats for arthropods and arachnids which, in turn, are fed upon by birds and bats. Arable topsoil that might have once covered the region is believed to have been disrupted - then eroded away - in the aftermath of the Ventral A Volcanic Event, exposing the comparatively saline and nutrient-poor quartz formations that undergirded them.
The Vibrano Expanse has an unusual geosonic feature: throughout the year, but especially during the spring and fall months, the whole region is suffused with an infrasonic hum caused by the unique conformation of the quartz deposits under the hills. It is believed that charges build up in naturally-formed capacitor-like crystal structures under the soil during the winter and summer particle radiation maximums in the adjacent Southern Tesseract. When the radiation begins to change polarity during the spring and fall, the charge is released in the form of vibrations in adjacent crystals via the piezoelectric effect. Creatures native to the region that normally hunt due to vibrations (i.e. spiders) and sound (i.e. bats) are specially-adapted to use the effects of this phenomenon to their advantage, gaining unparalleled spatial awareness during these seasons as their prey constitute 'gaps' in the othewise uniform soundscape. Infrasonics produced by the Vibrano Expanse are generally unpleasant to humanoid visitors, for whom the sound lies just outside of the usual hearing range. Rostrans, being more sensitive to air pressure in general than most humanoids, are particularly susceptible to sensations of vertigo or, on occasion, the sense of being 'watched' when visiting the Expanse. The howl of winds over the unusually regular landscape during the windy fall months amplifies the haunting aspect of the environment.
The quartz found in the Vibrano Expanse may eventually draw the attention of miners, as it would be useful in the production of electromechanical timers and sensors.