Question

some of the sand hills are mostly isolated from the rest like the one marked with a star. Other dunes line up to form a linear or sinuous ridge. Referring to fig. 15.2, what do we call a ridge of these kinds of dunes

Answer 1

A linear ridge of dunes is called a yardang, formed by wind erosion and aligned with the dominant wind direction. Yardangs and cross-bedding are important geological features that indicate environmental directions and past conditions.

Step-by-step explanation:

When we refer to a ridge made up of a linear alignment of dunes, we are generally talking about a feature called yardangs. These are formed by wind erosion and take shape in the direction of the prevailing winds. Yardangs can be observed both on Earth and on other celestial bodies, such as Mars, where similar erosional features have been identified.

The word yardang is of Turkic origin, and these features are especially prominent in arid environments where wind erosion is the dominant shaping force over the landscape. Cross-bedding is another related geological feature that can indicate the direction of wind or water flow and is often preserved in the rock record, providing valuable information about past environmental conditions. This type of bedding is formed as sediment is deposited on the steep sides of dunes or ripples one after another over time.