Monadnock: Isolated Hill Explained

The question describes a landform that is an isolated hill formed by a resistant rock type (felsic batholith) and revealed through the erosion of softer surrounding rocks. This specific geological feature is known as a Monadnock.

Identifying the Monadnock Landform

A Monadnock is a prominent, isolated remnant of rock, typically harder and more resistant than the surrounding landscape. It stands out because the weaker rocks around it have been worn away by weathering and erosion over long periods.

• Formation Process: Differential erosion is key. The resistant felsic batholith core remains while the less resistant country rock erodes down to a surrounding plain or lowlands.
• Characteristics: Appears as an isolated hill or small mountain rising abruptly from a flatter area.

Analyzing Other Geological Terms

Let's look at why the other options are not the correct answer:

• Hogback ridge: This is a long, narrow ridge with a sharp crest, often formed by the erosion of steeply dipping, resistant rock strata. It is typically linear, not an isolated hill.
• Flatiron: Similar to a hogback, this is a wedge-shaped ridge formed by erosion acting on dipping rock layers, often found in front of hogbacks. It's not defined by a resistant batholith core.
• Horst: This term refers to a block of Earth's crust that has been uplifted relative to the surrounding blocks, typically along faults. It's a tectonic feature, not primarily formed by differential erosion of a single rock body.

Based on the definition provided in the question (isolated hill, resistant felsic batholith, revealed by erosion), Monadnock is the correct term.