Really simple Hachuring:

Draw a short vertical line.

Draw a very thin horizontal teardrop shape.

Draw the area you want your mountain to be.

Select the mountain shape, and Path -> Path Effects

Add a Pattern Along Path effect. For a pattern source, copy the short line and paste it. For Pattern Copies select repeated, stretched. Set the spacing to something greater than 0, you can adjust it later.

Add another Pattern Along Path effect. Paste the teardrop as the pattern source, with 'Single Stretched' copies.

Set the whole thing to black with no border.

Adjust the spacing and width parameters of the two effects until it looks as you want it to. Width on the first is the width of the area covered by hachuring. Width on the second is the width of the individual strokes, and spacing on the first is the space between strokes.