What act on mountains to change their size height or surface?

Mountains are constantly shaped and changed by various geological processes and natural phenomena. Here are some factors that can alter their size, height, or surface:

1. Erosion: Erosion, caused by wind, water, ice, and gravity, wears down mountains over time, reducing their height and altering their shape. Factors such as rainfall, freeze-thaw cycles, and the movement of glaciers and rivers can contribute to erosion.

2. Plate Tectonics: The movement of tectonic plates, where mountains are formed through processes like continental collisions and subduction, can significantly influence their size and height. When plates collide, they can push landmasses upwards, creating mountain ranges like the Himalayas.

3. Volcanic Activity: Volcanic eruptions can add material to mountains, increasing their size and height. Lava flows and ash deposits can accumulate and form volcanic cones or shields, such as Mount Kilimanjaro in Africa.

4. Glaciation: The movement and melting of glaciers can shape mountain landscapes. Glaciers can erode mountains, creating valleys, cirques, and other glacial landforms. As they retreat, they can leave behind moraines and other deposits that alter the mountain's surface.

5. Weathering: Weathering processes, including temperature variations, freeze-thaw cycles, and chemical reactions, can cause rocks on mountains to break down, leading to changes in their surface texture and appearance.

6. Mass Wasting: Mass wasting refers to the downslope movement of soil and rock due to gravity. Processes like landslides, rockfalls, and debris flows can transport large amounts of material, altering mountain slopes and creating new features.

7. Human Activities: Human activities, such as mining, quarrying, and construction, can also modify mountains. Mining operations can remove significant amounts of material, changing the mountain's shape and size.

It's important to note that these processes often occur over long timescales, and the rate of change can vary depending on the specific region and geological conditions.