Endogenous Processes and Associated Landforms

Tensional forces causing faulting

Step 1: Block mountains (also called horsts) are formed by faulting, not folding. Step 2: When tensional forces pull the earth's crust apart, parallel faults are created. Step 3: The land between two parallel faults either rises upward (forming a block mountain or horst) or sinks downward (forming a rift valley or graben). Step 4: Option A is wrong — compression causes folding, which creates fold mountains like the Himalayas. Step 5: Option C describes volcanic mountains, and Option D describes residual/relict mountains. Classic Indian examples include the Vindhyas and Satpuras (block mountain

Graben or Rift Valley

Step 1: When tensional forces cause two parallel faults, the land between them can respond in two ways. Step 2: If the land between the faults rises, it forms a block mountain called a Horst — so Option A is wrong (horst rises, not sinks). Step 3: If the land sinks, it forms a depression called a Graben or Rift Valley — this is the correct answer. Step 4: Option B — a Nappe is the overthrust limb of a fold, completely unrelated to faulting depressions. Step 5: Option D — a Geosyncline is a shallow sea basin where sediments are deposited before fold mountains are formed. A famous example of a r

Six major plates

Step 1: The Plate Tectonic Theory as described in the chapter states that the earth is divided into six major plates. Step 2: These six plates are: (i) Pacific Plate, (ii) Eurasian Plate, (iii) American Plate, (iv) African Plate, (v) Australian Plate, and (vi) Antarctic Plate. Step 3: Each plate consists of the crust and upper mantle, extending up to 100 km in depth. Step 4: When two plates collide, their edges are pushed up to form great mountain ranges — this explains the formation of fold mountains. Step 5: It is important to memorise all six plate names as they are frequently asked in exam

Andes Mountains, South America

Step 1: The chapter classifies fold mountains as 'Young' or 'Old' based on when they were formed. Step 2: Young Fold Mountains were formed relatively recently in geological time and are still rugged, high, and some are still rising. Step 3: The chapter explicitly lists the Himalayas, Alps, Rockies, and Andes as Young Fold Mountains — so the Andes is correct. Step 4: Option A — the Aravallis are considered one of the oldest mountains on Earth, heavily eroded over time. Step 5: Options B and C — the Urals and Appalachians were formed during an earlier mountain-building period and are classified