In most earthquakes the Earth's crust cracks like porcelain, Stress builds up until a fracture forms at a line depth of a few kilometers and the crust slips to relieve the stress. Some earthquakes, however, take place hun dreds of kilometers down in the Earth's mantle, where high pressure makes rock so ductile that it flows instead of cracking, even under stress severe enough to deform it like putty. How can there be earthquakes at such depths?

    That such deep events do occur has been accepted only since 1927. when the seismologist Kiyoo Wadati convincingly demonstrated their existence. Instead of comparing the arrival times of seismic waves at different locations, as earlier researchers had done, Wadati relied on a time difference between the arrival of primary(P) waves and the slower secondary(S) waves. Because P and S waves travel at different but fairly constant speeds, the interval between their arrivals increases in proportion to the distance from the earthquake focus, or initial rupture point.

    For most earthquakes, wadati discovered, the interval was quite short near the epicenter; the point on the surface where shaking is strongest. For a few events, however, the delay was long even at the epicenter. Wadati saw a similar pattern when he analyzed data on the intensity of shaking. Most earthquakes had a small area of intense shaking, which weakened rapidly with increasing distance from the epicenter. but others were characterized by a lower peak intensity, felt over a broader area. Both the P-S intervals and the intensity patterns suggested two kinds of earthquakes: the more common shallow events, in which the focus lay just under the epicenter, and deep events, with a focus several hundred kilometers down.

    The question remained: how can such quakes occur, given that mantle rock at a depth of more than 50 kilometers is too ductile to store enough stress to fracture? Wadati's work suggested that deep events occur in areas (now called Wadati-Benioff zones) where one crustal plate is forced under another and descends into the mantle. The descending rock is substantially cooler than the surrounding mantle and(60) hence is less ductile and much more liable to fracture.

    In mid-February 1917 a women's movement independent of political affiliation erupted in Line New York City, the stronghold of the Socialist party in the United states. Protesting against the high cost of living, thousands of women refused to buy chickens, fish, and vegetables. The boycott shut down much of the City's foodstuffs marketing for two weeks, riveting public attention on the issue of food prices, which had increased partly as a result of increased exports of food to Europe that had been occurring since the outbreak of the First World War.

    By early 1917 the Socialist party had established itself as a major political presence in New York City. New York Socialists, whose customary spheres of struggle were electoral work and trade union organizing, seized the opportunity and quickly organized an extensive series of cost-of-living protests designed to direct the women's movement toward Socialist goals. Underneath the Socialists' brief commitment to cost-of-living organizing lay a basic indifference to the issue itself. While some Socialists did view price protests as a direct step toward socialism, most Socialists ultimately sought to divert the cost-of-living movement into alternative channels of protest. Union organizing, they argued, was the best method through which to combat the high cost of living. For others, cost-of-living or oganizing was valuable insofar as it led women into the struggle for suffrage, and similarly, the suffrage struggle was valuable insofar as it moved United States society one step closer to socialism.

    Although New York's Socialists saw the cost-of-living issue as, at best ,secondary or tertiary to the real task at hand, the boycotters, by sharp contrast, joined the price protest movement out of an urgent and deeply felt commitment to the cost-of-living issue. A shared experience of swiftly declining living standards caused by rising food prices drove these women to protest. Consumer organizing spoke directly to their daily lives and concerns; they saw cheaper food as a valuable end in itself. Food price protests were these women's way of organizing at their own workplace, as workers whose occupation was shopping and preparing food for their families.