PROJECT www.j aconline.com.au Draw a cross-section A cross-section shows the shape of a feature (such as a mountain) viewed from the side, as if cut through with a knife. Cross-sections are constructed using the contour lines on a topographic map. (You may like to refresh your memory about topographic maps by reading the information box on page 2 of this worksheet.) In this worksheet, you will draw two cross-sections from the topographical map of Mt Etna included on page 3. (You may find it easier to draw these if you first enlarge the map on a photocopier.) On completion, explain in a couple of paragraphs any similarities and differences in the two cross-sections, and what this tells you about the terrain in each case. Your cross-sections will be drawn between: • grid reference 227033 (name it A) and grid reference 252047 (name it B) • grid reference 239054 (name it C) and grid reference 241026 (name it D). In each case you will start and finish on a contour line. This will mean making a very minor adjustment for your start and finish points, once you have pinpointed your grid references. The following example is provided to remind you how to draw a cross-section. Drawing a cross-section 1. Line up the edge of a piece of plain paper along the line marked XY. 2. Make a small vertical mark on your paper where each contour line meets it. Also draw small marks below X and Y and label them X and Y. Near each vertical mark, write the height of the contour. (Use the contour interval to help you work this out.) 3. Line up your marked-up piece of paper against a graph you have drawn. Your graph should be exactly the same width as the length of the line between X and Y. Line up the X with the vertical axis of your graph. For each vertical mark on your piece of paper make a corresponding dot on your graph (to record the height of the contour above sea level). 4. Join the dots to create your cross-section. The first 18 have been plotted for you here. 5. Give your cross-section a title. If you wish, Map by MAPgraphics Pty Ltd, Brisbane Ltd, Pty MAPgraphics by Map you could shade the area under the line, so that the shape of your completed cross-section is clearer. © John Wiley & Sons Australia, Ltd 2005 2004-09-x-section.pdf (Page 1 of 2) PROJECT www.j aconline.com.au Topographic maps Topographic maps show the relief (height and shape) of the land using contours. They also show physical features such as forests, rivers and lakes and human-made features such as roads, railways and settlements. The key on a topographic map uses conventional signs to show the major features. Contour lines Contour lines are superimposed on topographic maps. These are numbered lines that join places of equal height above sea level on a map. Contours show the height, shape and location of hills and mountains in a landscape. The difference in height between one contour line and the next is always the same. This is known as the contour interval. On any contour map, evenly spaced contours mean an even slope, close contours mean a steeper slope and widely spaced contours mean a gentle slope or flat area. Spot heights are also given to show the actual height of particular locations. The highest points of a region are usually shown with spot heights. Grids on a topographic map A square grid is superimposed on topographic maps. These grids are numbered with two-digit numbers on the map’s margins. Lines that run up and down the map (north/south) are called eastings, because the numbers increase as you move east. The lines running across the map (east/west) are called northings because the numbers increase as you move north. Easting This six-figure grid reference of point X is and northing numbers can be put together to form a four-figure grid reference — the easting 23 6 04 6 is always given first (e.g. 2304). Four- and six-figure grid references From the eastings From the northings The four-figure area reference will tell you the grid square in which a feature will be found. To That is: 236046 pinpoint a more precise location of a feature, a six-figure grid reference is required. To work out the six-figure grid reference of a particular point on a map, you need to imagine that the distance between two eastings and two northings can be divided into 10 equal segments (tenths). These imaginary lines divide the spaces between one easting and the next into 10 equal columns, and the spaces between one northing and the next into 10 equal rows By way of example, an extract from the Mount Etna topographic map has been included above. You will note that the point to be identified (X) lies in the grid formed by eastings 23 and 24 and northings 04 and 05. Estimate on which imaginary lines between these two eastings and two northings this point is located. This will give you the third and sixth numbers respectively for your six-figure grid reference (e.g. 236046). Reference: SOSE Alive 3, pp. 108–9 ▪SOSE Alive Geography 2, pp. 12–13 © John Wiley & Sons Australia, Ltd 2005 2004-09-x-section.pdf (Page 2 of 2) 22 23 24 25 26 RANDAZZO 154 822 Passopisciaro Monte Calciniera 809 Linguaglossa 973 05 05 1632 967 583 Maletto 1632 1273 Monte Crisimo 1010 1345 1773 Monte Pizzillo 2414 BRONTE 1316 A 2934 2847 Nunziata Monte Etna 04 3323 Monte Scorsone Mascali 04 3000 1603 Monte Minardo 2942 1304 2500 B 2000 RIPOSTO 1734 GIARRE 2640 2182 Zafferana 742 1500 Etnea 1482 1284 Monte Piniteddu Santa Venerina 1398 03 ADRANO 03 1000 852 1039 Stazzo BIANCAVILLA San Tecla 262 Pedara Santa Maria Nicolosi 779 Aci Sene ACIREALE Trecastagni Antonio 500 Aci Platani 02 BELPASSO Mascalucia San 02 445 San Pietro Giovanni380 382 Clarenza Gravina di 200 PATERNO Aci Trezza Catania MEDITERRANEAN Aci Castello SEA MISTERBIANCO 325 N CATANIA Palermo Messina 22 23 24 25 26 Mt Etna 3323 m CATANIA Sicily Small built-up area or buildings Highway or Freeway Siracusa 500 Index contour line with height in metres Major road Contour line Minor road 1398 Spot height in metres Tracks Scale 1:250 000 Medium or dense forest Railway 0 5 10 15 kilometres Lava flow Built-up area Contour interval 100 metres Map by MAPgraphics Pty Ltd, Brisbane.