increasingly stronger as the air burst gradually turns into a surface burst. Much of the air shock will be transfomed. to a ground shock and eventually a crater wilf be formed.. To forfi a crater, i0elting and vaporization of the grormd due to the firebaflt'I .jt i r ),! Ei:g1:i:i.i r,nli':): Pag.: ] !j !l are, hovever, essentiar in addition to b1ast, severe d amage to heavily fcrtifiedundergror.md structures such as rnissife silos is in sei.ernl hFriawa/r tn 1" surface or subsurface bursts. a/ rll geilel''L 'e-!f,eveo ro requare b. The contour covered by overplessure of some particular magnitude is usuallyrepresented as a circl-e. In actu€J,ity there are a number of nodifying factorso vhichvould destroy this idealized shape. Most important among these a1'e terrain effectssuch as hills, trees or buildings in a populated area. large hi11y 1and, forinstance, vill increase air blast effects in some areas and decrease them in others.These shielding effects will not, however, be dependent upon line of sighteonside"ations, since the blast lrifl ''bend around corners", "bend over tops", enter,:through srnalI holesrr, etc. Hence no space vhich is direcily connected with the atmosphere one way or another vill escape the overpressure. \,U:ren blast is reflectedagainst a nountain side, a va.l-1 - exterior or interior - of a house or a simifarobject, the result will sonetimes be a 1ocal increase" sornetines a decrease. Theoverpressure at the refl-ecting surface night reach several times the peak value ofthe incident bfast wave. The exact overpressure patterns will^ hence be quite conplicated. in a built-up area or a hil-l_y, forested landscape. lamage c,aus ed. by air blast
**Analysis**
The text appears to be discussing the effects of a surface burst, likely a nuclear explosion, on the surrounding environment and structures. The language used is technical and scientific, indicating a focus on the physical and destructive consequences of such an event. The text also touches on the complexities of air blast waves and their interactions with terrain, buildings, and other obstacles.

**Category**
Science and technology, Humanitarian aid and relief