Editing Harris matrix (section)

===Example===
[[File:Harris section example.jpg]]

Take this hypothetical [[Archaeological section|section]] as an example of matrix formation. Here there are twelve [[Archaeological context|contexts]], numbered thus:
#A horizontal layer
#[[Masonry wall]] remnant
#Backfill of the wall construction [[cut (archaeology)|cut]] (sometimes called construction [[trench]])
#A horizontal layer, probably the same as 1
#Construction cut for wall 2
#A clay floor [[Relationship (archaeology)|abutting]] wall 2
#Fill of shallow cut 8
#Shallow pit cut
#A horizontal layer
#A horizontal layer, probably the same as 9
#Natural sterile ground formed before human occupation of the site
#Trample in the base of cut 5 formed by workmen's boots constructing the structure wall 2 and floor 6 is [[Archaeological association|associated]] with.

The order in which these events occurred and the reverse order they should have been excavated with would be demonstrated by the following Harris matrix.

====Completed matrix====
[[File:Harris matrix example.jpg|thumb|left]]
[[File:Example of a simple stratigraphic sequence as visualised using a Harris matrix diagram.png|thumb|320x320px|Example of a simple stratigraphic sequence, as visualised using a Harris matrix diagram]]
The later a context's formation is, the higher it is in the matrix, and conversely the earlier it is, the lower. [[Relationship (archaeology)|Relationships]] between contexts are recorded in the sequence of formation, so even though wall 2 is physically higher than other contexts in section, its position in the matrix is immediately under backfill 3 and below floor 6. This is because the formation of the backfill and floor happened later. Also note the matrix splits into two parts below the construction cut 5. This is because the relationships across the section have been destroyed by the cutting of construction cut 5 and even if it is likely that layers 1 and 4 are probably the same deposit the information can not be guaranteed if the only information we had was this section. However the position of cut 5 and natural layer 11 "ties" the matrix together above and below the split in the matrix.

====Interpretation====
Starting at the bottom, the order events occurred in this section is revealed by the matrix as follows. Natural ground formation 11 was followed by the laying down of layers 9 and 10 which "probably" occurred as the same event. Then a shallow pit 8 was cut and then back filled with 7. This pit [[feature (archaeology)|feature]] in turn was "sealed" by the laying down of layer 1 which is probably the same event as layer 4. Following this a major change in land use occurs as construction cut 5 is dug and immediately followed by trample off the feet of people 12 working in the construction cut 5 who then build wall 2 after which they backfill excess space between the wall 2 and cut 5 with backfill 3. Finally clay floor 6 is laid down to the right of wall 2 over backfill 3 indicating a probable interior surface.

The nature of archaeological investigation and the subjective nature of all human experience means that a degree of interpretive activity obviously occurs during the process of excavation. The Harris matrix itself however serves to provide a check on observable quantifiable physical phenomena and relies on the excavator understanding which way in the sequence is 'up' and the ability of the excavator to excavate and record honestly, accurately and stratigraphically. The process of excavation destroys the context and requires the excavator to be able and willing to make informed (by experience and where necessary collaboration) decisions about which context or contexts lay at the top of the sequence.

As long as [[Excavation (archaeology)#Common errors in excavation|undercutting]] is not endemic, in practice onsite errors in judgment should become evident especially if temporary sections are kept for [[Archaeological section#Stratigraphic control|stratigraphic control]] in areas of a site that are hard to discern. However, archaeological sections, while being useful and valuable, only ever present a slice or caricature of a sequence, and often underrepresent its complexity. The use of archaeological sections when dealing with stratigraphic complexity is limited and their use should be context-sensitive rather than as a running arbiter of sequence.

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